Liquid radiation curable resins capable of curing into layers with selective visual effects and methods for the use thereof

ABSTRACT

The invention relates to a method for forming a liquid radiation curable resin capable of curing into a solid upon irradiation comprising at least one thermally sensitive visual effect initiator. The liquid radiation curable resin is capable of curing into three-dimensional articles having selective visual effects. The resulting three-dimensional articles possess excellent color and/or transparency stability and excellent mechanical properties.

FIELD OF THE INVENTION

The present invention relates to radiation curable resins suitable foruse in forming three dimensional articles using additive fabricatingprocesses.

BACKGROUND OF THE INVENTION

Additive fabrication processes for producing three dimensional articlesare known in the field. Additive fabrication processes utilizecomputer-aided design (CAD) data of an object to build three-dimensionalparts layer-by-layer. These three-dimensional parts may be formed fromliquid resins, powders, or other materials.

A non-limiting example of an additive fabrication process isstereolithography (SL). Stereolithography is a well-known process forrapidly producing models, prototypes, patterns, and production pasts incertain applications. SL uses CAD data of an object wherein the data istransformed into thin cross-sections of a three-dimensional object. Thedata is loaded into a computer which controls a laser beam that tracesthe pattern of a cross section through a liquid radiation curable resincomposition contained in a vat, solidifying a thin layer of the resincorresponding to the cross section. The solidified layer is recoatedwith resin and the laser beam traces another cross section to hardenanother layer of resin on top of the previous layer. The process isrepeated layer by layer until the three-dimensional object is completed.When initially formed, the three-dimensional object is, in general, notfully cured and therefore may be subjected to post-curing, if required.An example of an SL process is described in U.S. Pat. No. 4,575,330.

The liquid radiation curable resin used in stereolithography and otheradditive fabrication processes for forming three-dimensional objects canbe solidified by light energy. Typically, liquid radiation curableresins are cured by ultra-violet (UV) light. Such light is typicallyproduced by lasers (as in stereolithography), lamps, or light emittingdiodes (LEDs). See PCT Patent Application PCT/US10/60677, filed on Dec.16, 2010, and incorporated by reference in its entirety. The delivery ofenergy by a laser in a stereolithography system can be Continuous Wave(CW) or Q-switched pulses. CW lasers provide continuous laser energy andcan be used in a high speed scanning process.

With known resins, it is typical that the final color and/or claritydevelops in the three dimensional article as it is cured. Known resinsmay be clear in liquid forms and form opaque three-dimensional articlesupon cure. Other known resins may be colorless in liquid form andcapable of curing into colored three-dimensional articles. Furthermore,some resins appear as a first color in liquid form and turn a secondcolor upon cure.

Throughout this patent application the term color is defined as follows:color (or colour, alternative spelling) is the visual perceptualproperty corresponding in humans to the categories called red, yellow,green, etc. Black is the visual perception of absence of all color,whereas white is the visual perception of all colors. Color derives fromthe spectrum of light (distribution of light energy versus wavelength)interacting in the eye with the spectral sensitivities of the lightreceptors. Color categories and physical specification of color are alsoassociated with objects, materials, light sources, etc., based on theirphysical properties such as light absorption, reflection, or emissionspectra. Typically, only features of the composition of light that aredetectable by humans (wavelength spectrum for 400 nm to 700 nm, roughly)are included, thereby objectively relating the psychological phenomenonof color to its physical specification.

Color and transparency are two distinct principles. For instance,something may visually appear perfectly clear and still colored. Forinstance, certain colored glass is entirely transparent to the eye andpossesses a color. Similarly, something may be colorless and also clearor opaque. Colorless is defined as lacking all color. For instance, pureliquid water is clear and colorless. An article that is visuallyperceived as perfectly clear and as a color, for instance, blue, isreflecting the blue color while allowing all other wavelengths of lightto pass through. When a viewer perceives white, the article will appearless transparent because all colors are being reflected back at theviewer and thus not passing through the article.

In recent years, the demand for liquid radiation curable resins thatproduce three-dimensional articles that have excellent dimensionalaccuracy, shape stability, mechanical properties, and the like hasincreased. Along with this development, demand has grown forthree-dimensional articles that possess a desired color ortransparency/opacity, and also have the mentioned excellent properties.The colored three-dimensional articles are useful because they areaesthetically pleasing, can mimic the appearance of commercialmaterials, and may possess light-shielding properties. Along with thisdevelopment, the demand for radiation-curable compositions in which thecolor or opacity can be selectively controlled during curing has alsoincreased.

Meeting the challenges of producing selectively coloredthree-dimensional articles is described in U.S. Pat. No. 6,133,336,issued Oct. 17, 2000 and assigned to Zeneca Limited. This patentdescribes a method of curing and adding color to a three-dimensionalarticle using light at a single wavelength, and at a lower and a higherdose. The lower dose of light is used to cure the liquid resin to form asolid and the higher dose of light is used to add color to the resin.The process claimed is only for adding color, not removing color. Thispatent also claims a composition for a photocurable and photocolorableresin. However, the disclosed composition has poor mechanical propertiesand poor color stability. For instance, after initial curing, theuncolored sections of the article become colored over time in ambientlight. Such problems are common with photoresponsive coloringtechniques.

U.S. Pat. No. 5,677,107, assigned to Spectra Group Limited, Inc.,discloses a method for preparing and selectively coloring athree-dimensional article by adding or removing color. The coloringagent is photoresponsive and the method claimed is dependent on using aphotoresponsive coloring agent.

U.S. Pat. No. 5,942,554, assigned to Spectra Group Limited, Inc.,discloses a method of effecting color change in polymeric bodies ofeither thermal curable or photocurable resins. The color-changingcompound is sensitive to acid produced during polymerization of theresin. The acid is produced from the initiating species which areactivated by either light or temperature. The color change occurs whenthe coloring agent is exposed to the acid.

U.S. Pat. No. 6,664,024, assigned to American Dye Source, Inc., disclosea photocurable resin composition for forming three-dimensional objectsthat can be selectively colored that utilized a photoactivated coloringcompound.

U.S. Pat. No. 6,649,311, assigned to Vantico Limited, discloses a resinfor use in forming three-dimensional objects that can use aphotosensitive coloring compound contained in microcapsules. Similarly,U.S. Published Patent Application No. 2004/0076909 discloses a liquidresin composition for use in forming three-dimensional objects whichcomprises particle dispersed in the composition which are micro-capsulescontaining a photosensitive color changing composition.

U.S. Published Patent Application No. 2004/0170923, assigned to 3DSystems, Inc., discloses colored resins useful in formingthree-dimensional objects; however, such resins cannot be selectivelycolored by exposure to various doses of light.

U.S. Pat. No. 6,746,814, assigned to the inventor, discloses a methodfor selectively coloring or shading an article produced by overexposingthe liquid resin to radiation during cure and then heating the entiremodel with an effective amount of heat in order to induce a color changein the overexposed sections of the article. No coloring or transparencymodifying agent is used.

It would be desirable to develop a liquid radiation curable resin thatcan cure into a three-dimensional article wherein the color and/ortransparency of the three-dimensional article can be selectivelycontrolled to be substantially clear and/or colorless in some areas andhave a desired color and/or transparency in other areas while havingexcellent mechanical properties. Moreover, it would be desirable todevelop a liquid radiation curable resin wherein the color and/ortransparency of the selectively controlled sections remain at asubstantially constant color or no color, and/or transparency over time.

SUMMARY OF THE INVENTION

The first aspect of the instant claimed invention is a method of forminga three-dimensional article having at least one selectively coloredand/or transparent region comprising subjecting a liquid radiationcurable resin comprising at least one thermally sensitive visual effectinitiator having an activation temperature to appropriate imagingradiation to form a three-dimensional article layer by layer, whilesimultaneously selectively controlling the temperature of the liquidradiation curable resin so that at least one portion of the liquidradiation curable resin is at or above the activation temperature of thethermally sensitive visual effect initiator to thereby form the at leastone selectively colored and/or transparent region of thethree-dimensional article.

The second aspect of the instant claimed invention is athree-dimensional article having at least one selectively colored and/ortransparent region made using an additive fabrication process, wherein aliquid radiation curable resin used to create the article comprises fromabout 0.005 wt % to about 5 wt % of at least one thermally sensitivevisual effect initiator.

The third aspect of the instant claimed invention is a liquid radiationcurable resin wherein the liquid radiation curable resin compositioncomprises at least two thermally sensitive visual effect initiators.

The fourth aspect of the instant claimed invention is a method offorming a three-dimensional article having regions of selective colorand/or transparency from a liquid radiation curable resin comprising thesteps:

curing a layer of a liquid radiation curable resin using light, therebyforming a cored solid polymeric layer;

irradiating selected areas of the cured solid polymeric layer resultingfrom step (a), a previously cured solid polymeric layer, or a layer ofthe liquid radiation curable resin with a higher dose of light than usedin a step (a) thereby removing color and/or altering the transparency ofthe areas irradiated with the higher dose of light.

repeating steps (a) and (b) on a previously cured solid polymeric layeror a layer of the liquid radiation curable resin, as necessary, untilthe desired three-dimensional article having selectively colored and/ortransparent regions is formed;

wherein the wavelength(s) of light in each of steps (a) and (b) are thesame, and step (b) can be performed before, during, or after step (a).

The fifth aspect of the instant claimed invention is a method of forminga three-dimensional article having selectively colored and/ortransparent regions made from a liquid radiation curable resin whereinthe coloration and/or transparency of the selectively colored and/ortransparent regions is created by selectively controlling thetemperature of the liquid radiation curable resin.

The sixth aspect of the instant claimed invention is a three-dimensionalarticle having colored and uncolored sections produced via an additivefabrication process that when exposed to fluorescent light for 30 daysat ambient temperature attains a ΔE* measured throughout the exposure tofluorescent light that remains within 50% of the ΔE* measured on thefirst day of the exposure to fluorescent light, preferably the ΔE*measured through the exposure to fluorescent light remains within 30% ofthe ΔE* measured on the first day of the exposure to fluorescent light,more preferably the ΔE* measured through the exposure to fluorescentlight remains within 15% of the ΔE* measured on the first day of theexposure to fluorescent light, even more preferably the ΔE* measuredthrough the exposure to fluorescent light remains within 10% of the ΔE*measured on the first day of the exposure to fluorescent light.

The seventh aspect of the instant claimed invention is a method offorming a three-dimensional article having selectively colored and/ortransparent regions from a liquid radiation curable resin comprising thesteps of

-   -   a. selectively curing a layer of liquid radiation curable resin        with at least two different doses of light thereby forming a        cured solid layer with selectively colored and/or transparent        regions    -   b. juxtaposing at least two cured solid layers formed from        step (a) in order to form a three-dimensional article.

The eight aspect of instant claimed invention is a liquid radiationcurable resin composition capable of curing into a solid uponirradiation comprising from 0.005 wt % to 5 wt % of at least onethermally sensitive visual effect initiator, preferably from 0.005 wt %to 3 wt. %, more preferably from 0.005 wt % to 2.5 wt. %, even morepreferably from 0.005 wt % to 1 wt % even more preferably from 0.005 wt% to 0.5 wt %, of the at least one thermally sensitive visual effectinitiator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, FIG. 2, FIG. 3, and FIG. 4 show cured three-dimensional articlesillustrative of the invention.

FIG. 5 shows cured three-dimensional articles illustrative of theinvention on the left in comparison to examples of the current state ofthe art on the right after initial cure (top), and after exposure tofluorescent light for 30 days (bottom).

DETAILED DESCRIPTION OF THE INVENTION

This application claims priority from U.S. Provisional PatentApplication 61/297,467 filed Jan. 22, 2010 and U.S. Provisional patentApplication 61/392,153 filed Oct. 12, 2010, both hereby incorporated byreference in their entirety.

Throughout this patent application, a thermally sensitive visual effectinitiator is defined as a component capable of incorporation into aliquid radiation curable resin that can be used to formthree-dimensional objects and that upon cure is capable of creating achange in the color or transparency of a three-dimensional article madetherefrom in response to temperature. Generally, thermally sensitivevisual effect initiators can be placed into one or both of twocategories: 1) components that affect color; and 2) components thataffect transparency.

The activation temperature of a thermally sensitive visual effectinitiator is defined as the temperature at which the thermally sensitivevisual effect initiator component begins to exhibit a color and/ortransparency change. The locking temperature of a thermally sensitivevisual effect initiator is the temperature at which any change in colorand/or transparency of the thermally sensitive visual effect initiator,or the liquid resin or three-dimensional article made therefrom when athermally sensitive visual effect initiator is incorporated into aliquid radiation curable resin, will be permanent or semi-permanent.Permanent color change is irreversible color change. Semi-permanentcolor change is reversible under certain circumstance; i.e. to reversethe color change the thermochromic component would have to be cooledsignificantly below room temperature. Non-permanent color change is anycolor change that occurs that is not permanent or semi-permanent.Non-permanent color change is reversible.

Throughout this patent application, thermochromism is defined as theability of a substance to change color due to a change in temperature. Athermochromic component is a component capable of incorporation into aliquid radiation curable resin that has the ability to change color dueto a change in temperature. A thermally sensitive transparency modifieris a component capable of incorporation into a liquid radiation curableresin that has the ability to change the transparency of a liquidradiation curable resin or a three dimensional article made therefromdue to a change in temperature. The transparency is typically changed bymodifying the light scattering properties of the selectively curedsection of the three-dimensional article produced from a liquidradiation curable resin. A thermochromic component can also be athermally sensitive transparency modifier and a thermally sensitivetransparency modifier can also be a thermochromic component. In fact,even a component that is substantially thermochromic will often alsoaffect the visual transparency of the three-dimensional article in somesmall way. A thermally sensitive visual effect initiator may be athermochromic component, a thermally sensitive transparency modifier, orboth.

Throughout this patent application, a microcapsule is a tiny particlecapable of encapsulating other components. The heat of polymerization ofthe resin is the heat given off by the exothermic reaction ofpolymerization. Intensity is defined as the time-averaged power per unitarea. Dose is the total power per unit area.

The first aspect of the instant claimed invention is a method of forminga three-dimensional article having at least one selectively coloredand/or transparent region comprising subjecting a liquid radiationcurable resin comprising at least one thermally sensitive visual effectinitiator having and activation temperature to appropriate imagingradiation to form a three-dimensional article layer by layer, whilesimultaneously selectively controlling the temperature of the liquidradiation curable resin so that at least one portion of the liquidradiation curable resin is at or above the activation temperature of thethermally sensitive visual effect initiator to thereby form the at leastone selectively colored and/or transparent region of thethree-dimensional article. Appropriate imaging radiation is radiationsufficient to cure a liquid radiation curable resin layer by layer inorder to form a three-dimensional article. In an embodiment, thethermally sensitive visual effect initiator is a thermochromiccomponent. In another embodiment, the thermally sensitive visual effectinitiator is a thermally sensitive transparency modifier. In anotherembodiment, the thermally sensitive visual effect initiator is both athermochromic component and a thermally sensitive transparency modifier.In further embodiments, the liquid radiation curable compositioncomprises a mixture of various thermally sensitive visual effectinitiators.

To selectively control the color and/or transparency of a liquidradiation curable resin comprising a thermally sensitive visual effectinitiator, the resin temperature must reach the activation temperatureof the thermally sensitive visual effect initiator, and preferably reachthe locking temperature. In order to reach the activation and lockingtemperatures in selected areas, the local temperature of the resin inselect areas must be selectively controlled. A thermally sensitivevisual effect initiator of any activation or locking temperature may beused as long as the local temperature of the liquid radiation curableresin can be appropriately controlled in selected areas.

The local temperature of the resin is dependent on the heat ofpolymerization of the liquid radiation curable resin, the amount ofliquid radiation curable resin polymerized, and any heating or coolingprovided by outside sources, such as heating elements on the additivefabrication machine. A selective visual effect can be created bycontrolling the local temperature in any one, or a combination, of theseways.

The heat of polymerization of a liquid radiation curable resin isdependent on the composition of the resin. The heat of polymerization ofmany compounds can be found in Brandrup et al, Polymer Handbook, 4thEdition, 2003. Depending on the type of additive fabrication machineused, a lower heat of polymerization can be somewhat compensated for byaltering the vat temperature, if a vat is present on the particularmachine, or local heating element, if present on the particular machine,by providing a greater dose of light, or by increasing the layerthickness.

The heat of polymerization of a liquid radiation curable resin can bemeasured using Differential Scanning Calorimeter (DSC), for instance, aTA Instruments Differential Scanning Calorimeter Model Q2000 with aphotocalorimeter accessory (PCA) model S2000. For example, a 10 mgsample can be place in a Tzero aluminum pan. The sample should be heldisothermally at 30° C. for 1 minute to mimic a typical curingtemperature of a liquid radiation curable resin. The sample can the beilluminated for 6 sec with an appropriate light source, for example a200 W mercury arc lamp with appropriate filter, for instance a 365 nmfilter, at 500 mW/cm². It is preferred that liquid radiation curableresins that produce greater than approximately 145+/−20 J/g at 500mW/cm² be used for the instant claimed invention. However, liquidradiation curable resins that produce less head could be used in theinstant claimed invention by increasing the dose of light, thickness oflayer cured, or adjusting various parameters of the additive fabricationmachine that may affect temperature (such as vat temperature or theoutput of a local heating element).

The amount of resin polymerized is dependent on the dose of lightdelivered to the liquid radiation curable resin and the thickness of thelayer cured. A higher amount of energy being transferred to each areawill initiate more polymerization in that area of the liquid radiationcurable resin composition. The increased amount of polymerization willresult in an increased temperature in that area, thus enabling the localtemperature of the area to be selectively controlled. Generally, a resinthat has a lower heat of polymerization will require a thicker layer becured, thus initiating more polymerization per layer and raising thelevel of heat produced. Similarly, resins with higher critical energy(Ec) and lower depth of penetration (Dp) values, as determined by theworking curve method well known in the art, may require thicker layersand/or a higher light dose to be built in order achieve the requisitelocal temperature to selectively control the color and/or transparencyof the three-dimensional article.

The local temperature can be at least partially controlled by adjustingvarious parameters on the additive fabrication machine. In an embodimentwhere the particular type of additive fabrication machine used has avat, for instance a stereolithography machine, the temperature is aleast partially controlled by adjusting the vat temperature and byadjusting the intensity of light used to cure the liquid radiationcurable resin. In another embodiment, the temperature of the thermallysensitive visual effect initiator is controlled by a local heatingelement at the location of polymerization and by adjusting the intensityof light used to cure the liquid radiation curable resin. In a furtherembodiment, the local temperature is controlled only by a local heatingelement. If a stereolithography machine is not used, similar setting foradjusting the resin temperature, light intensity, or local heatingelement can be adjusted to impact the local temperature of the resin. Onsome stereolithography machines, the light intensity can be controlledby increasing or decreasing the layer hatch overcure on the selectedareas of the resin. The layer hatch overcure is the amount of energythat is being put into the layer. The machine setting called layer hatchovercure may be referred to differently on different stereolithographymachine makes and models. The stereolithography machine uses the layerhatch overcure to calculate the light source power and speed to form theproper layer. Those skilled in the art of additive fabrication machineoperation know how to adjust an additive fabrication machine in order tomanipulate the liquid radiation curable resin temperature and the lightintensity in certain areas. A single light source or multiple lightsources may be used to cure and/or heat the liquid radiation curableresin.

The use of thermally sensitive visual effect initiators has severaladvantages over the current state of the art. Firstly, the thermallysensitive visual effect initiators can be used with a hybrid curingsystem. A hybrid curing system is a curing system consisting offree-radical and cationic photoinitiators along with free-radical andcationic polymerizable components. When a non-hybrid system is subjectto irradiation in order to form a three-dimensional article, the formedthree-dimensional article possesses undesirable physical properties.Hybrid systems allow for three-dimensional articles that possessexcellent mechanical properties. In the current state of the art ofliquid radiation curable resin for additive fabrication that are capableof selective coloration in an additive fabrication process, for instancein U.S. Pat. No. 6,133,336, halochromic components are used effectuatethe selective coloring. Halochromic components change color based pH.Such components are not effective with a hybrid curing system unlessthey can be appropriately contained and shielded from the acid presentduring cationic polymerization. If the halochromic components are notappropriately contained, for instance in a microcapsule impermeable toacid, the acid created from the cationic photoinitiating system willreact with the halochromic components and cause the halochromiccomponents to change color. Thermochromic components can be made to bemuch more acid-stable than certain photosensitive or halochromiccoloring agents and are thus able to work in a hybrid curing system. Inan embodiment, a non-hybrid curing system is used. In anotherembodiment, a hybrid curing system is used. In an embodiment, thethermally sensitive visual initiator does not undergo any significantvisual color or transparency change in response to the acid producedduring the polymerization of the liquid radiation curable resin. In anembodiment the thermally sensitive visual effect initiator comprises amicrocapsule that is impermeable to acid. In another embodiment thethermally sensitive visual effect initiator comprises a microcapsulethat is substantially impermeable to acid.

Second, the longevity of the selective coloring in a selectively coloredthree-dimensional article can be much greater with a thermally sensitivevisual effect initiator than with current state of the art coloringcomponents capable of selective coloration. Thermally sensitive visualeffect initiators may or may not be photosensitive, or may be much lessphotosensitive than other photosensitive coloring agents. Articles thatare selectively colored using current state of the art coloringcomponents capable of selective coloration are often subject to whatappears to be color bleeding. Furthermore, the color immediately aftercure changes substantially as time progresses after cure. This occursbecause, as the halochromic or photosensitive coloring agents areexposed to ambient light, the coloring agent, or the developer orphotoinitiator that activates the coloring agent in the case of certainhalochromic coloring systems, is triggered in ambient light. This leadsto additional unwanted color forming over time in the uncoloredsections. Articles that are selectively colored using thermallysensitive visual effect initiators, which are generally notphotosensitive, are subject to less color bleeding. Moreover, sucharticles possess substantially the same color as time progresses aftercure as they do immediately after core. In an embodiment, the thermallysensitive visual effect initiator is not photosensitive. In anotherembodiment, the thermally sensitive visual effect initiator is slightlyphotosensitive.

In an embodiment, the thermally sensitive visual effect initiator is amicrocapsule that contains a thermally sensitive component orcomponents. The origin of the visual effect can occur from changes inlight absorption, light reflection, and/or light scattering withtemperature. Thermally sensitive visual effect initiators can be presentin various types of compounds. A write-up of thermochromism in polymerscan be found in Thermochromic Phenomena in Polymers.© 2008 Arno Seebothand Detlef Lötzsch. Additional information concerning thermochromiccompounds can be found in Organic Photochromic and ThermochromicCompounds, Volume 2,© 1999 John C. Crano and Robert J. Guglielmetti.Examples of thermochromic components can be found in U.S. Pat. Nos.7,304,008, 6,008,269, and 4,424,990, and in WO/2009/137709. Otherthermochromic compounds can be found in, for instance, Japanese patentpublications 2005-220201, 2007-332232, 2003-313453, 2001-242249,10-152638, 03-076783, 03-076786, and 1522236.

Surprisingly, a thermally sensitive visual effect initiator can beincorporated into a liquid radiation curable resin without anysubstantial reduction in the mechanical properties of the resin. In anembodiment, the thermally sensitive visual effect initiator isincorporated into a liquid radiation curable resin by mixing thethermally sensitive visual effect initiator into the liquid radiationcurable resin. In an embodiment, the thermally sensitive visual effectinitiator is incorporated into a liquid radiation curable resin bymixing the liquid radiation curable resin into the thermally sensitivevisual effect initiator. In an embodiment, the thermally sensitivevisual effect initiator is incorporated into the liquid radiationcurable resin along with the solvent which contains the thermallysensitive visual effect initiator and, in another embodiment, withoutthe solvent.

To determine the appropriate amount of thermally sensitive visual effectinitiator to use in a liquid radiation curable resin composition, avisual inspection of the part after cure can be made. The amount ofthermally sensitive visual effect initiator in the liquid radiationcurable resin composition is largely a function of visual preference.However, if too much or too little of the thermally sensitive visualeffect initiator is incorporated into the liquid radiation curable resincomposition, the selectively colored sections of the cured article maynot be sufficiently distinct or the cured article may not besufficiently transparent or opaque. As the particle size of thethermally sensitive visual effect initiator is reduced, more thermallysensitive visual effect initiator can be added to have sufficientlydistinct selectively colored/uncolored and/or transparent/opaqueportions of the cured article. In an embodiment, the thermally sensitivevisual effect initiator is present in an amount less than about 5 wt %.In another embodiment the amount of thermally sensitive visual effectinitiator is less than about 1 wt %. In another embodiment the amount ofthermally sensitive visual effect initiator is less than about 0.5 wt %.In another embodiment the amount of thermally sensitive visual effectinitiator is less than about 0.2 wt %. In another embodiment the amountof thermally sensitive visual effect initiator is less than about 0.1 wt%. In another embodiment the amount of thermally sensitive visual effectinitiator is about 0.1 wt %. In another embodiment, the amount ofthermally sensitive visual effect initiator is about 0.024 wt %.

In another embodiment, the amount of thermally sensitive visual effectinitiator is present in an amount from about 0.005 wt % to about 5 wt %.In another embodiment, the amount of thermally sensitive visual effectinitiator is present in an amount from about 0.005 wt % to about 3 wt %.In another embodiment, the amount of thermally sensitive visual effectinitiator is present in an amount from about 0.005 wt % to about 2 wt %.In another embodiment, the amount of thermally sensitive visual effectinitiator is present in an amount from about 0.005 wt % to about 1 wt %.In another embodiment, the amount of thermally sensitive visual effectinitiator is present in an amount from about 0.01 wt % to about 5 wt %.In another embodiment, the amount of thermally sensitive visual effectinitiator is present in an amount from about 0.05 wt % to about 5 wt %.In another embodiment, the amount of thermally sensitive visual effectinitiator is present in an amount from about 0.01 wt % to about 2 wt %.

In an embodiment, the thermally sensitive visual effect initiator isincorporated into Somos® WaterClear® Ultra 10122 liquid radiationcurable resin. In another embodiment, the thermally sensitive visualeffect initiator is incorporated into Somos® WaterShed® XC 11122 liquidradiation curable resin. Somos® WaterClear® Ultra 10122 and Somos®WaterShed® XC 11122 are liquid radiation curable resins manufactured byDSM Desotech, Inc. Both Somos® WaterClear® Ultra 10122 and Somos®Watershed® XC 11122 are substantially colorless and transparent afterfull cure. Somos® WaterClear® Ultra 10122 comprises between 45-70 wt. %of epoxies, 10-25 wt % of acrylates, 5-15 wt % of oxetane, 5-15 wt % ofpolyol, 5-15 wt % of photoinitiators, and 0-10 wt % of additives. Somos®WaterShed® XC 11122 comprises between 45-70 wt % of epoxies, 5-20 wt %of acrylate, 10-25 wt % of oxetane, 5-15 wt % of photoinitiators, and0-10 wt % of additives.

In an embodiment, the thermally sensitive visual effect initiator is athermochromic component. The thermochromic component generally operatesto change the visually perceived color of the cured three-dimensionalarticle, but the component may also have some effect on the transparencyof the cured three-dimensional article. The use of thermochromiccomponents comprising microcapsules in an ink composition that ispolymerizable with UV light is disclosed in U.S. Pat. No. 5,500,040,incorporated herein by reference in its entirety. However, this patentdoes not mention the use of thermochromic components in liquid radiationcurable resins for additive fabrication or the production ofthree-dimensional articles with selective visual effects. R. A. M.Hikmet and R. Polesso have demonstrated that the reflective propertiesof a cholesteric liquid crystal gel incorporated into a liquid radiationcurable resin may be controlled by polymerizing the liquid radiationcurable resin at various temperatures. The polymerization is used tolock in the orientation of the liquid crystals that have been aligned bythe exposure to a certain temperature so that subsequent changes intemperature do not significantly change the color. Please see R. A. M.Hikmet and R. Polesso, “Patterned Multicolor Switchable CholestericLiquid Crystal Gels,” Advanced Materials, 2002, 14, No. 7, April 4,hereby incorporated by reference. No methods of making curedthree-dimensional objects having selectively colored regions arediscussed.

In an embodiment, the thermochromic component is contained inThermolock® 79s Pink to Clear, manufactured by Matsui Shikiso ChemicalCo., Ltd., http://www.matsui-color.com/. Thermolock® 79s Pink to Clearis an ink containing thermochromic components. The thermochromiccomponents are microcapsules containing thermally sensitive ink.Thermolock® 79s Pink to Clear contains thermochromic componentsincorporated into ethylcyclohexane and other components. Thermolock® 79sPink to Clear utilizes microcapsules containing a leuco dye and othercomponents. Thermolock® 79s Pink to Clear comprises about 50-53 wt % ofethylcyclohexane, about 14 wt % of thermochromic component, about 15 wt% of 2-butoxyethyl acetate, less than 0.1 wt % of formaldehyde, andother ingredients. Ethylcyclohexane evaporates over time onceThermolock® 79s Pink to Clear is exposed to air. Whenever a wt % ofThermolock® 79s Pink to Clear is referred to in this application, the wt% refers to Thermolock® 79s Pink to Clear before any substantialevaporation of ethylcyclohexane. In other embodiments, the thermochromiccomponent turns from some other color to clear. For instance, the colormay be blue, red, or green contained in Thermolock® 79s Blue to Clear,Thermolock® 79s Red to Clear, and Thermolock® 79s Green to Clear,respectively.

In an embodiment, the thermochromic component is present in an amountless than about 5 wt % of the liquid radiation curable resin. In anotherembodiment the amount of thermochromic component is less than about 1 wt%. In another embodiment the amount of thermochromic component is lessthan about 0.5 wt %. In another embodiment the amount of thermochromiccomponent is less than about 0.2 wt %. In another embodiment the amountof thermochromic component is less than about 0.1 wt %. In anotherembodiment the amount of thermochromic component is about 0.1 wt %. Inanother embodiment, the amount of thermochromic component is about 0.024wt %.

In another embodiment, the amount of thermochromic component is presentin an amount from about 0.005 wt % to about 5 wt % of the liquidradiation curable resin. In another embodiment, the amount ofthermochromic component is present in an amount from about 0.005 wt % toabout 3 wt %. In another embodiment, the amount of thermochromiccomponent is present in an amount from about 0.005 wt % to about 2 wt %.In another embodiment, the amount of thermochromic component is presentin an amount from about 0.005 wt % to about 1 wt %. In anotherembodiment the amount of thermochromic component is present in an amountfrom about 0.01 wt % to about 5 wt %. In another embodiment, the amountof thermochromic component is present in an amount from about 0.05 wt %to about 5 wt %. In another embodiment, the amount of thermochromiccomponent is present in an amount from about 0.01 wt 5 to about 2 wt %.

Thermolock®0 79s Pink to Clear changes from a first color to no colorwhen subjected to a certain increase in temperature. The activationtemperature of Thermolock® 79s Pink to Clear is about 65° C. and thelocking temperature is about 79° C. Once the locking temperature isreached, the color change can be reversed by lowering the temperature toabout −10° C. In an embodiment, a thermochromic component thatirreversibly changes color is used. In another embodiment, thethermochromic component that is incorporated into the liquid radiationcurable resin is capable of changing from a first color to a secondcolor due to a certain increase in temperature. In another embodiment,the thermochromic component is capable of changing from no color to afirst color due to a certain increase in temperature.

In an embodiment, Thermolock® 79s Pink to Clear is combined withcommercially available Somos® WaterClear® Ultra 10122 liquid radiationcurable resin. In another embodiment, Thermolock® 79s Pink to Clear iscombined with commercially available Somos® WaterShed® XC 11122 liquidradiation curable resin. In another embodiment, Thermolock® 79s Pink toClear is combined with a filled liquid radiation curable resin. Filledresins are liquid radiation curable resins that comprise a substantialamount of filler and are usually opaque or substantially opaque aftercure. In an embodiment, Thermolock® 79s Pink to Clear is present in anamount less than about 5 wt % of the liquid radiation curable resincomposition. In another embodiment the amount of Thermolock® 79s Pink toClear is less than about 1 wt %. In another embodiment, the amount ofThermolock® 79s Pink to Clear is about 0.3 wt %. FIGS. 1 and 2 showcured three-dimensional articles produced from a liquid radiationcurable resin composition of 99.7 wt % Somos® WaterShed® XC 11122 and0.3 wt % Thermolock® 79s Pink to Clear.

In an embodiment, the thermochromic component is contained inThermolock® 80s. Thermolock® 80s is a commercially available inkcontaining thermochromic components, filler, and other pigments.Thermolock®80s is available from Matsui Shikiso Chemical Co. Ltd. and isthe ink used in the Thermolock® Marker 80, also available from MatsuiShikiso Chemical Co. Ltd. Thermolock® 80s contains the samethermochromic components as Thermolock® 79s Pink to Clear, but alsoincorporates other pigments to effectuate a visible color change of redto yellow.

Thermolock® 80s can be incorporated into a liquid radiation curableresin. A commercially available Thermolock® Marker 80 can be obtained.The marker can then be disassembled by using, for example, a razorbladeto disassemble the marker. The felt tip of the marker can then beremoved and the ink extracted. The ink can then be poured into a liquidradiation curable resin. More than one Thermolock® Marker 80 may beneeded depending on the batch size. The liquid radiation curable resinand Thermolock® 80s can the be combined by mixing.

In an embodiment, Thermolock® 80s is combined with commerciallyavailable Somos® WaterClear® Ultra 10122 liquid radiation curable resin.In another embodiment, Thermolock® 80s is combined with commerciallyavailable Somos® WaterShed® XC 11122 liquid radiation curable resin.Somos® WaterClear® Ultra 10122 liquid radiation curable resin and Somos®WaterShed® XC 11122 liquid radiation curable resin are substantiallytransparent after full cure. In another embodiment, Thermolock® 80s iscombined with a filled liquid radiation curable resin. In an embodiment,Thermolock® 80s is present in an amount less than about 5 wt % of theliquid radiation curable resin composition. In another embodiment theamount of Thermolock® 80s is less than about 1 wt %. In anotherembodiment, the amount of Thermolock® 80s is about 0.3 wt %.

In another embodiment, the liquid radiation curable resin comprises atleast one thermally sensitive transparency modifier, which may also be athermochromic component. The thermally sensitive transparency modifiermay operate by modifying how light passes through the three-dimensionalarticle. This light scattering effect causes the article to becomeopaque or substantially opaque in certain sections. If thethree-dimensional article is clear and colorless in sections where thethermally sensitive transparency modifier is not activated, the articlemay appear to be white in sections where the transparency has beenmodified. This is because the modification to the transparency causeslight to reflect back at the viewer, thus producing the white color. Thereduction in transparency can be controlled depending on the amount ofthermally sensitive opacity modifier incorporated into the liquidradiation curable resin, or the local temperature of the liquidradiation curable resin.

In an embodiment, the thermally sensitive transparency modifier is athermally expandable microsphere present in an amount from about 0.005wt % to about 5 wt %. When the activation temperature of the thermallyexpandable microsphere is reached, the thermally expandable microsphereexpands. The expansion causes the scattering of light passing throughthe three-dimensional article and creates an increasingly opaqueappearance in the three-dimensional article. This opaque appearance canbe selectively controlled by controlling the local temperature of theliquid radiation curable resin as it is being cured.

In an embodiment, the thermally sensitive transparency modifier is athermally expandable microsphere. In an embodiment, the thermallyexpandable microsphere is in the form of an Expancel® unexpandedmicrosphere product produced by AkzoNobel NV. Please seehttp://www.akzonobel.com/expancel/. Detailed descriptions of variousexpandable microspheres and their production can be found in, forexample, U.S. Pat. Nos. 3,615,972, 3,945,956, 4,287,308, 5,536,756,6,235,800, 6,235,394 and 6,509,384, in EP 486080, EP 1054034, EP 1288272and EP1408097, in WO 2004/072160, and in Japanese publication laid openNo. 1987-286534. In an embodiment, the thermally expandable microsphereis a dry unexpanded microsphere. In an embodiment, the thermallysensitive transparency modifier is Expancel® 031 DU 40. In anotherembodiment, the thermally sensitive transparency modifier is Expancel®820 DU 40. The activation and locking temperatures are the same for theExpancel® line of expandable microspheres. The activation and lockingtemperatures for Expancel® 031 DU 40 and Expancel® 820 DU 40 isapproximately 75° C., with a maximum activation and locking temperatureof approximately 115° C. In another embodiment, the thermally sensitivetransparency modifier is Expancel® 551 DU 40. The activation and lockingtemperatures for Expancel® 551 DU 40 is approximately 95-100° C., with amaximum activation and locking temperature of approximately 139-147° C.

Thermally expandable microspheres have previously been used in liquidradiation curable resins used in three-dimensional object formation.Please see Japanese Patent Application laid open 2-116537. The use ofthermally expandable microspheres has previously been used to controlwarping or shrinkage as the three-dimensional object is formed. ThisJapanese patent application discusses the use of thermally expandablemicrospheres in a liquid radiation curable resin and discusses addingthermal energy to the resin during curing in order to initiate theappropriate amount of expansion. No discussion is made as to onlyinitiating expansion of the thermally expandable microspheres in certainareas or to selectively control the expansion of the microspheres incertain locations so as to produce the visual effect of a selectivelytransparent article. Likewise, the control of the local temperature ofthe liquid radiation curable resin during polymerization so as to onlyinitiate thermal expansion in certain areas of the curedthree-dimensional object is not mentioned. The use of collapsiblemicrospheres is also known in liquid radiation curable resins in orderto control the effects of temperature on the three-dimensional object ininvestment casting applications. Please see, for example, U.S. Pat. No.5,176,188 and U.S. Pat. No. 5,364,889, both assigned to DSM IP AssetsBV.

The amount of thermally sensitive transparency modifier incorporatedinto a liquid radiation curable resin is dependent on the size of themicrospheres. With smaller microspheres, a greater amount of thermallysensitive transparency modifier must be included to effectuate theselective change in transparency. In an embodiment, the thermallysensitive transparency modifier is present in an amount less than about5 wt % of the liquid radiation curable resin composition. In anotherembodiment the amount of thermally sensitive transparency modifier isless than about 1 wt %. In another embodiment, the amount of thermallysensitive transparency modifier is about 0.5 wt %. In anotherembodiment, the amount of thermally sensitive transparency modifier isless than about 0.5 wt %. In another embodiment, the amount of thermallysensitive transparency modifier is about 0.1 wt %. In anotherembodiment, the amount of thermally sensitive transparency modifier isfrom about 0.005 to about 0.25 wt %.

In another embodiment, the amount of thermally sensitive transparencymodifier is present in an amount from about 0.005 wt % to about 5 wt %.In another embodiment, the amount of thermally sensitive transparencymodifier is present in an amount from about 0.005 wt % to about 3 wt %.In another embodiment, the amount of thermally sensitive transparencymodifier is present in an amount from about 0.005 wt % to about 2 wt %.In another embodiment, the amount of thermally sensitive transparencymodifier is present in an amount from about 0.005 wt % to about 1 wt %.In another embodiment, the amount of thermally sensitive transparencymodifier is present in an amount from about 0.01 wt % to about 5 wt %.In another embodiment, the amount of thermally sensitive transparencymodifier is present in an amount from about 0.05 wt % to about 5 wt %.In another embodiment, the amount of thermally sensitive transparencymodifier is present in an amount from about 0.01 wt % to about 2 wt. %.

In an embodiment, the thermally sensitive transparency modifier isincorporated into a substantially clear liquid radiation curable resin.In another embodiment, the thermally sensitive transparency modifier isincorporated into a substantially clear and colorless liquid radiationcurable resin. FIG. 3 and FIG. 4 show two example compositions wherein athermally sensitive transparency modifier has been incorporated into asubstantially clear and colorless liquid radiation curable resin. Inboth FIG. 3 and FIG. 4, the liquid radiation curable resin used to curethe pictured three-dimensional objects comprises approximately 0.1 wt %of Expancel 031 DU 40 and approximately 99.9 wt % of Somos® WaterClear®Ultra 10122. In FIG. 3, the white appearance of the teeth is created byachieving the activation temperature of the thermally sensitivetransparency modifier in those regions. Similarly, in FIG. 4 the whiteappearance of the bones in the hand is created by achieving theactivation temperature of the thermally sensitive transparency modifierin those regions.

In another embodiment, more than on thermally sensitive visual effectinitiator is incorporated into the liquid radiation curable resincomposition. In one embodiment, each of the more than one thermallysensitive visual effect initiators has the same activation and/orlocking temperature. In another embodiment, at least one of the morethan one thermally sensitive visual effect initiator has an activationtemperature and/or a locking temperature which is different than theother thermally sensitive visual effect initiator or initiators. In thisembodiment, additional colors and/or transparencies are achieved bycontrolling the temperature of the resin to activate color and/ortransparency change, add color and/or opacity, or remove color and/oropacity in only some of the thermally sensitive visual effectinitiator(s) in some areas while activating color and/or transparencychange, adding color and/or opacity, or removing color and/or opacity inall or none of the thermally sensitive visual effect initiator(s) inother areas. The color and/or transparency of the liquid radiationcurable resin before may or may not be the same as any part of the curedthree-dimensional article.

In accordance with an embodiment of the invention, the liquid radiationcurable resin comprises a thermally sensitive visual effect initiator, afree radical polymerizable component, and a photoinitiating systemcapable of initiating free radical polymerization. In anotherembodiment, the liquid radiation curable resin comprises a thermallysensitive visual effect initiator, a cationic polymerizable component,and a photoinitiating system capable of initiating cationicpolymerization. In a further embodiment, the liquid radiation curableresin comprises a thermally sensitive visual effect initiator, a freeradical polymerizable component, a photoinitiating system capable ofinitiating free radical polymerization, a cationic polymerizablecomponent, and a photoinitiating system capable of initiating cationicpolymerization.

In accordance with an embodiment of the invention, the liquid radiationcurable resin of the invention may comprise at least one free-radicalpolymerizable component, that is, a component which undergoespolymerization initiated by free radicals. The free-radicalpolymerizable components are monomers, oligomers, and/or polymers; theyare monofunctional or polyfunctional materials, i.e., have 1, 2, 3, 4,5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 100, or more functional groups thatcan polymerize by free radical initiation, may contain aliphatic,aromatic, cycloaliphatic, arylaliphatic, heterocyclic moiety(ies), orany combination thereof. Examples of polyfunctional materials includedendritic polymers such as dendrimers, linear dendritic polymers,dendrigraft polymers, hyperbranched polymers, star branched polymers,and hypergraft polymers; see US 2009/0093564 A1. The dendritic polymersmay contain one type of polymerizable functional group or differenttypes of polymerizable functional groups, for example, acrylates andmethacrylate functions.

Examples of free-radical polymerizable components include acrylates andmethacrylates such as isobornyl (meth)acrylate, bornyl (meth)acrylate,tricyclodecanyl (meth)acrylate, dicyclopentanyl (meth)acrylate,dicyclopentenyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl(meth)acrylate, 4-butylcyclohexyl (meth)acrylate, acryloyl morpholine,(meth)acrylic acid, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl (meth)acrylate, methyl (meth)acrylate,ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate,butyl (meth)acrylate, amyl (meth)acrylate, isobutyl (meth)acrylate,t-butyl (meth)acrylate, pentyl (meth)acrylate, caprolactone acrylate,isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate,octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl(meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl(meth)acrylate, tridecyl (meth)acrylate, undecyl (meth)acrylate, lauryl(meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate,tetrahydrofurfuryl (meth)acrylate, butoxyethyl (meth)acrylate,ethoxydiethylene glycol (meth)acrylate, benzyl (meth)acrylate,phenoxyethyl (meth)acrylate, polyethylene glycol mono(meth)acrylate,polypropylene glycol mono(meth)acrylate, methoxyethylene glycol(meth)acrylate, ethoxyethyl (meth)acrylate, methoxypolyethylene glycol(meth)acrylate, methoxypolypropylene glycol (meth)acrylate, diacetone(meth)acrylamide, beta-carboxyethyl (meth)acrylate, phthalic acid(meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl(meth)acrylate, butylcarbamylethyl (meth)acrylate, n-isopropyl(meth)acrylamide fluorinated (meth)acrylate, 7-amino-3,7-dimethyloctyl(meth)acrylate.

Example of polyfunctional free-radical polymerizable components includethose with (meth)acryloyl groups such as trimethylolpropanetri(meth)acrylate, pentaerythritol (meth)acrylate, ethylene glycoldi(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate,dicyclopentadiene dimethanol di(meth)acrylate,[2-[1,1-dimethyl-2-[(1-oxoallyl)oxy]ethyl]-5-ethyl-1,3-dioxan-5-yl]methylacrylate;3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecanedi(meth)acrylate; dipentaerythritol monohydroxypenta(meth)acrylate,propoxylated trimethylolpropane tri(meth)acrylate, propoxylatedneopentyl glycol di(meth)acrylate, tetraethylene glycoldi(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,4-butanedioldi(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycoldi(meth)acrylate, polybutanediol di(meth)acrylate, tripropyleneglycoldi(meth)acrylate, glycerol tri(meth)acrylate, phosphoric acid mono- anddi(meth)acrylate, C₇-C₂₀ alkyl di(meth)acrylate,tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate,tris(2-hydroxyethyl)isocyanurate di(meth)acrylate, pentaerythritoltri(meth)acrylate, pentaerythritol tetra(meth)acrylate,dipentaerythritol hexa(meth)crylate, tricyclodecane diyl dimethyldi(meth)acrylate and alkoxylated versions (e.g., ethoxylated and/orpropoxylated) of any of the preceding monomers, and alsodi(meth)acrylate of a diol which is an ethylene oxide or propylene oxideadduct to bisphenol A, di(meth)acrylate of a diol which is an ethyleneoxide or propylene oxide adduct to hydrogenated bisphenol A, epoxy(meth)acrylate which is a (meth)acrylate adduct to bisphenol A ofdiglycidyl ether, diacrylate of polyoxyalkylated bisphenol A, andtriethylene glycol divinyl ether, and adducts of hydroxethyl acrylate.

In accordance with an embodiment, the polyfunctional (meth)acrylates ofthe polyfunctional component may include all methacryloyl groups, allacryloyl groups, or any combination of methacryloyl and acryloyl groups.In an embodiment, the free-radical polymerizable component is selectedfrom the group consisting of bisphenol A diglycidyl etherdi(meth)acrylate, ethoxylated or propoxylated bisphenol A or bisphenol Fdi(meth)acrylate, dicyclopentadiene dimethanol di(meth)acrylate,[2-[1,1-dimethyl-2-[(1-oxoallyl)oxy]ethyl]-5-ethyl-1,3-dioxan-5-yl]methylacrylate, dipentaerythritol monohydroxypenta(meth)acrylate,dipentaerythritol hexa(meth)acrylate, propoxylated trimethylolpropanetri(meth)acrylate, and propoxylated neopentyl glycol di(meth)acrylate,and any combination thereof.

In another embodiment, the free-radical polymerizable component isselected from the group consisting of bisphenol A diglycidyl etherdiacrylate, dicyclopentadiene dimethanol diacrylate,[2-[1,1-dimethyl-2-[(1-oxoallyl)oxy]ethyl]-5-ethyl-1,3-dioxan-5-yl]methylacrylate, dipentaerythritol monohydroxypentaacrylate, propoxylatedtrimethylolpropane triacrylate, and propoxylated neopentyl glycoldiacrylate, and any combination thereof.

In specific embodiments, the liquid radiation curable resin compositionsof the invention include one or more of bisphenol A diglycidyl etherdi(meth)acrylate, dicyclopentadiene dimethanol di(meth)acrylate,dipentaerythritol monohydroxypenta(meth)acrylate, propoxylatedtrimethylolpropane tri(meth)acrylate, and/or propoxylated neopentylglycol di(meth)acrylate, and more specifically one or more of bisphenolA diglycidyl ether diacrylate, dicyclopentadiene dimethanol diacrylate,dipentaerythritol monohydroxypentaacrylate, propoxylatedtrimethylolpropane triacrylate, and/or propoxylated neopentyl glycoldiacrylate.

The liquid radiation curable resin composition can include any suitableamount of the free-radical polymerizable component, for example, incertain embodiments, in an amount up to about 95% by weight of thecomposition, in certain embodiments, up to about 50% by weight of thecomposition, and in further embodiments from about 5% to about 25% byweight of the composition.

In all embodiments, the liquid radiation curable resin composition ofthe present invention includes a photoinitiating system. Thephotoinitiating system can be a free-radical photoinitiator or acationic photoinitiator or a photoinitiator that contains bothfree-radical initiating function and cationic initiating functions onthe same molecule. The photoinitiator is a compound that chemicallychanges due to the action of the light or the synergy between the actionof light and the electronic excitation of a sensitizing dye to produceat least one of a radical, an acid, and a base.

Typically, free radical photoinitiators are divided into those that formradicals by cleavage, know as “Norrish Type I” and those that formradicals by hydrogen abstraction, know as “Norrish type II”. The Norrishtype II photoinitiators require a hydrogen donor, which serves as thefree radical source. As the initiation is based on a bimolecularreaction, the Norrish type II photoinitiators are generally slower thanNorrish type I photoinitiators which are based on the unimolecularformation of radicals. On the other hand, Norrish type IIphotoinitiators possess better optical absorption properties in thenear-UV spectroscopic region. Photolysis of aromatic ketones, such asbenzophenone, thioxanthones, benzil, and quinones, in the presence ofhydrogen donors, such as alcohols, amines, or thiols leads to theformation of a radical produced from the carbonyl compound (ketyl-typeradical) and another radical derived from the hydrogen donor. Thephotopolymerization of vinyl monomers is usually initiated by theradicals produced from the hydrogen donor. The ketyl radicals areusually not reactive toward vinyl monomers because of the sterichindrance and the delocalization of an unpaired electron.

To successfully formulate a liquid radiation curable resin composition,it is necessary to review the wavelength sensitivity of thephotoinitiator(s) present in the composition to determine if they willbe activated by the method and wavelength of irradiation chosen to curethe composition.

In accordance with an embodiment, the liquid radiation curable resincomposition includes at least one free radical photoinitiator, e.g.,those selected from the group consisting of benzoylphosphine oxides,aryl ketones, benzophenones, hydroxylated ketones, 1-hydroxyphenylketones, ketals, metallocenes, and any combination thereof.

In an embodiment, the liquid radiation curable resin compositionincludes at least one free-radical photoinitiator selected from thegroup consisting of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and2,4,6-trimethylbenzoyl phenyl, ethoxy phosphine oxide,bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide,2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1,2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone,2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one,4-benzoyl-4′-methyl diphenyl sulphide, 4,4′-bis(diethylamino)benzophenone, and 4,4′-bis(N,N′-dimethylamino) benzophenone (Michler'sketone), benzophenone, 4-methyl benzophenone, 2,4,6-trimethylbenzophenone, dimethoxybenzophenone, 1-hydroxycyclohexyl phenyl ketone,phenyl (1-hydroxyisopropyl)ketone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone,4-isopropylphenyl(1-hydroxyisopropyl)ketone,oligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl] propanone],camphorquinone, 4,4′-bis(diethylamino) benzophenone, benzil dimethylketal, bis(eta 5-2-4-cyclopentadien-1-yl)bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl] titanium, and any combinationthereof.

For light sources emitting in the 300-475 nm wavelength range,especially those emitting at 365 nm, 390 nm, or 395 nm, examples ofsuitable free-radical photoinitiators absorbing in this area include:benzoylphosphine oxides, such as, for example, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Lucirin TPO from BASF) and2,4,6-trimethylbenzoyl phenyl, ethoxy phosphine oxide (Lucirin TPO-Lfrom BASF), bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (Irgacure819 or BAPO from Ciba),2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1 (Irgacure 907from Ciba), 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone (Irgacure 369 from Ciba),2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one(Irgacure 379 from Ciba), 4-benzoyl-4′-methyl diphenyl sulphide(Chivacure BMS from Chitec), 4,4′-bis(diethylamino) benzophenone(Chivacure EMK from Chitec), and 4,4′-bis(N,N′-dimethylamino)benzophenone (Michler's ketone). Also suitable are mixtures thereof.

Additionally, photosensitizers are useful in conjunction withphotoinitiators in effecting cure with light sources emitting in thiswavelength range. Examples of suitable photosensitizers include:anthraquinones, such as 2-methylanthraquinone, 2-ethylanthraquinone,2-tertbutylanthraquinone, 1-chloroanthraquinone, and2-amylanthraquinone, thioxanthones and xanthones, such as isopropylthioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, and1-chloro-4-propoxythioxanthone, methyl benzoyl formate (Darocur MBF fromCiba), methyl-2-benzoyl benzoate (Chivacure OMB from Chitec),4-benzoyl-4′-methyl diphenyl sulphide (Chivacure BMS from Chitec),4,4′-bis(diethylamino) benzophenone (Chivacure EMK from Chitec).

It is possible for UV light sources to be designed to emit light andshorter wavelengths. For light sources emitting at wavelengths frombetween about 100 and about 300 nm, it is desirable to employ aphotosensitizer with a photoinitiator. When photosensitizers, such asthose previously listed are present in the formulation, otherphotoinitiators absorbing at shorter wavelengths can be used. Examplesof such photoinitiators include: benzophenones, such as benzophenone,4-methyl benzophenone, 2,4,6-trimethyl benzophenone, anddimethoxybenzophenone, and, 1-hydroxyphenyl ketones, such as1-hydroxcyclohexyl phenyl ketone, phenyl (1-hydroxyisopropyl)ketone,2-hydroxy-1-[4-(2-hroxyethoxy) phenyl]-2-methyl-1-propanone, and4-isopropylphenyl(1-hydroxyisopropyl)ketone, benzil dimethyl ketal, andoligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl] propanone](Esacure KIP 150 from Lamberti).

Light sources can also be designed to emit visible light. For lightsources emitting light at wavelengths from about 475 nm to about 900 nm,examples of suitable free radical photoinitiators include:camphorquinone, 4,4′-bis(diethylamino) benzophenone (Chivacure EMK fromChitec), 4,4′-bis(N,N′-dimethylamino) benzophenone (Michler's ketone),bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (Irgacure 819 or BAPOfrom Ciba), metallocenes such as bis (eta 5-2-4-cyclopentadien-1-yl) bis[2,6-difluoro-3-(1H-pyrrol-1-yl) phenyl] titanium (Irgacure 784 fromCiba), and the visible light photoinitiators from Spectra Group Limited,Inc. such as H-Nu 470, H-Nu-535, H-Nu-635, H-Nu-Blue-640, andH-Nu-Blue-660.

The liquid radiation curable resin composition can include any suitableamount of the free-radical photoinitiator, for example, in certainembodiments, in an amount up to about 15% by weight of the composition,in certain embodiments, up to about 10% by weight of the composition,and in further embodiments from about 1% to about 5% by weight of thecomposition. In other embodiments, the amount of free-radicalphotoinitiator is present in an amount of from about 1 wt % to about 8wt % of the total composition, more preferable from about 1 wt % toabout 6 wt % of the total composition.

In accordance with an embodiment, liquid radiation curable resincompositions of the invention comprise at least one cationicallypolymerizable component, that is, a component which undergoespolymerization initiated by cations or in the presence of acidgenerators. The cationically polymerizable components may be monomers,oligomers, and/or polymers, and may contain aliphatic, aromatic,cycloaliphatic, arylaliphatic, heterocyclic moiety(ies), and anycombination thereof. Suitable cyclic ether compounds can comprise cyclicether groups as side groups or groups that form part of an alicyclic orheterocyclic ring system.

The cationic polymerizable component is selected from the groupconsisting of cyclic ether compounds, cyclic acetal compounds, cyclicthioethers compounds, spiro-orthoester compounds, cyclic lactonecompounds, and vinyl ether compounds, and any combination thereof.

Examples of cationically polymerizable components include cyclic ethercompounds such as epoxy compounds and oxetanes, cyclic lactonecompounds, cyclic acetal compounds, cyclic thioether compounds, spiroorthoester compounds, and vinylether compounds. Specific examples ofcationically polymerizable components include bisphenol A diglycidylether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether,brominated bisphenol A diglycidyl ether, brominated bisphenol Fdiglycidyl ether, brominated bisphenol S diglycidyl ether, epoxy novolacresins, hydrogenated bisphenol A diglycidyl ether, hydrogenatedbisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether,3,4-epoxycyclohexymethyl-3′,4′-epoxycyclohexanecarboxylate,2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)-cyclohexane-1,4-dioxane,bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene oxide,4-vinylepoxycyclohexane, vinylcyclohexene dioxide, limonene oxidelimonene dioxide, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate,3,4-epoxy-6-methylcyclohexyl-3′,4′-epoxy-6′-methylcyclohexanecarboxylate,ε-caprolactone-modified 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylates, trimethylcaprolactone-modified, 3,4epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylates,β-methyl-δ-valerolactone-modified,3,4-epoxycyclohexcylmethyl-3′,4′-epoxycyclohexane carboxylates,methylenebis(3,4-epoxycyclohexane), bicyclohexyl-3,3′-epoxide,bis(3,4-epoxycyclohexyl) with a linkage of —O—, —S—, —SO₂—, —C(CH₃)₂—,—CBr₂—, —C(CBr₃)₂—, —C(CF₃)₂—, —C(CCl₃)₂—, or —CH(C₆H₅)—,dicyclopentadiene diepoxide, di(3,4-epoxycyclohexylmethyl) ether ofethylene glycol, ethylenebis(3,4-epoxycyclohexanecarboxylate),epoxyhexhydrodioctylphthalate, epoxyhexahydro-di-2-ethylhexyl phthalate,1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether,neopentylglycol diglycidyl ether, glycerol triglycidyl ether,trimethylolpropane triglycidyl ether, polyethylene glycol diglycidylether, polypropylene glycol diglycidyl ether, polyglycidyl ethers ofpolyether polyol obtained by the addition of one or more alkylene oxidesto aliphatic polyhydric alcohols such as ethylene glycol, propyleneglycol, and glycerol, diglycidyl esters of aliphatic long-chain dibasicacids, monoglycidyl ethers of aliphatic higher alcohols, monoglycidylethers of phenol, cresol, butyl phenol, or polyether alcohols obtainedby the addition of alkylene oxide to these compounds, glycidyl esters ofhigher fatty acids, epoxidated soybean oil, epoxybutylstearic acid,epoxyoctylstearic acid, epoxidated linseed oil, epoxidatedpolybutadiene, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene,3-ethyl-3-hydroxymethyloxetane,3-ethyl-3-(3-hydroxypropyl)oxymethyloxetane,3-ethyl-3-(4-hydroxybutyl)oxymethyloxetane,3-ethyl-3-(5-hydroxypentyl)oxymethyloxetane,3-ethyl-3-phenoxymethyloxetane, bis(1-ethyl(3-oxetanyl))methyl)ether,3-ethyl-3-((2-ethylhexyloxy)methyl)oxetane,3-ethyl-((triethoxysilylpropoxymethyl)oxetane,3-(meth)-allyloxymethyl-3-ethyloxetane,(3-ethyl-3-oxetanylmethoxy)methylbenzene,4-fluoro-[1-(3-ethyl-3-oxetanylmethoxy)methyl]benzene,4-methoxy-[1-(3-ethyl-3-oxetanylmethoxy)methyl]-benzene,[1-(3-ethyl-3-oxetanylmethoxy)ethyl]phenyl ether,isobutoxymethyl(3-ethyl-3-oxetanylmethyl)ether,2-ethylhexyl(3-ethyl-3-oxetanylmethyl)ether, ethyldiethyleneglycol(3-ethyl-3-oxetanylmethyl)ether, dicyclopentadiene(3-ethyl-3-oxetanymethyl)ether,dicyclopentenyloxyethyl(3-ethyl-3-oxetanylmethyl)ether,dicyclopentenyl(3-ethyl-3-oxetanylmethyl)ether,tetrahydrofurfuyl(3-ethyl-3-oxetanylmethyl)ether,2-hydroxyethyl(3-ethyl-3-oxetanylmethyl)ether,2-hydroxypropyl(3-ethyl-3-oxetanylmethyl)ether, and any combinationthereof. Examples of polyfunctional materials that are cationicallypolymerizable include dendritic polymers such as dendrimers, lineardendritic polymers, dendrigraft polymers, hyperbranched polymers, starbranched polymers, and hypergraft polymers with epoxy or oxetanefunctional groups. The dendritic polymers may contain one type ofpolymerizable functional group or different types of polymerizablefunctional groups, for example, epoxy and oxetane functions.

In embodiments of the invention, the cationic polymerizable component isat least one selected from the group consisting of a cycloaliphaticepoxy and an oxetane. In a specific embodiment, the cationicpolymerizable component is an oxetane, for example, an oxetanecontaining 2 or more than 2 oxetane groups. In another specificembodiment, the cationic polymerizable component is a cycloaliphaticepoxy, for example, a cycloaliphatic epoxy with 2 or more than 2 epoxygroups.

In an embodiment, the epoxide is3,4-epoxycyclohexylmethyl-3′,4-epoxycyclohexanecarboxylate (available asCELLOXIDE™ 2021P from Daicel Chemical, or as CYRACURE™ UVR-6105 from DowChemical), hydrogenated bisphenol A-epichlorohydrin based epoxy resin(available as EPONEX™ 1510 from Hexion), 1,4-cyclohexanedimethanoldiglycidyl ether (available as HELOXY™ 107 from Hexion), a mixture ofdicyclohexyl diepoxide and nanosilica (available as NANOPOX™), and anycombination thereof.

The above-mentioned cationically polymerizable compounds can be usedsingly or in combination of two or more thereof.

The liquid radiation curable resin composition can include any suitableamount of the cationic polymerizable component, for example, in certainembodiments, in an amount an amount up to about 95% by weight of thecomposition, in certain embodiments, up to about 50% by weight of thecomposition, and in further embodiments from about 5% to about 25% byweight of the composition. In other embodiments the amount ofcationically polymerizable components if from about 10 wt % to about 80wt % of the total composition.

In accordance with an embodiment, the polymerizable component of theliquid radiation curable resin composition is polymerizable by bothfree-radical polymerization and cationic polymerization. An example ofsuch a polymerizable component is a vinyloxy compound, for example, oneselected from the group consisting of bis(4-vinyloxybutyl)isophthalate,tris(4-vinyloxybutyl) trimellitate, and combination thereof.

In accordance with an embodiment, the liquid radiation curable resincomposition includes a photoinitiating system that is a photoinitiatorhaving both cationic initiating function and free radical initiatingfunction. In accordance with an embodiment, the liquid radiation curableresin composition includes a cationic photoinitiator. The cationicphotoinitiator generates photoacids upon irradiation of light. Theygenerate Brönsted or Lewis acids upon irradiation.

The cationic photoinitiator triaryl sulfoniumtetrakis(pentafluorophenyl) borate is available from Bayer/Ciba. Triarylsulfonium tetrakis(pentafluorophenyl) borate can be used either as thecationic photoinitiator present in the photocurable composition or incombination with other cationic photoinitiators. In an embodiment,triaryl sulfonium tetrakis(pentafluorophenyl) borate is used incombination with sulfonium antimonate type photoinitiators.

In an embodiment, any suitable cationic photoinitiator can be used, forexample, those selected from the group consisting of onium salts,halonium salts, iodosyl salts, selenium salts, sulfonium salts,sulfoxonium salts, diazonium salts, metallocene salts, isoquinoliniumsalts, phosphonium salts, arsonium salts, tropylium salts,dialkylphenacylsulfonium salts, thiopyrilium salts, diaryl iodoniumsalts, triaryl sulfonium salts, sulfonium antimonate salts, ferrocenes,di(cyclopentadienyliron)arene salt compounds, cyclohexeneoxidecompounds, and pyridinium salts, and any combination thereof. Oniumsalts, e.g., iodonium salts, sulfonium salts and ferrocenes, have theadvantage that they are thermally stable. Thus, any residualphotoinitiator does not continue to cure after the removal of theirradiating light. Cationic photoinitiator offer the advantage that theyare not sensitive to oxygen present in the atmosphere.

The liquid radiation curable resin composition of the invention includesat least one cationic photoinitiator, wherein the cationicphotoinitiator is selected from the group consisting of aromaticdiazonium salts, aromatic sulfonium salts, aromatic iodonium salts,metallocene based compounds, aromatic phosphonium salts and silanolaluminium complexes, and any combination thereof. In an embodiment, thecationic photoinitiator is selected from the group consisting ofaromatic sulfonium salts, aromatic iodonium salts, and metallocene basedcompounds, and any combination thereof. In another embodiment, thecationic photoinitiator is selected from the group consisting oftriarylsulfonium salts, diaryliodonium salts, and metallocene basedcompounds, and any combination thereof.

In particular embodiment, the cationic photoinitiator has an anionselected from the group consisting of BF₄ ³¹ , AsF₆ ⁻, SbF₆ ⁻, PF₆ ⁻,B(C₆F₅)₄ ⁻, perfluoroalkysulfonates, perfluoroalkylphosphates, andcarborane anions.

In an embodiment, the cationic photoinitiator has a cation selected fromthe group consisting of aromatic sulfonium salts, aromatic iodoniumsalts, and metallocene based compounds with at least an anion selectedfrom the group consisting of SbF₆ ⁻, PF₆ ⁻, B(C₆F₅)₄ ⁻,perfluoroalkylsulfonates, perfluoroalkylphosphates, and (CH₆B₁₁Cl₆)⁻.

In a particular embodiment, the cationic photoinitiator is an aromaticsulfonium salt based cationic photoinitiator selected from the groupconsisting of 4-(4-benzoylphenylthio)phenyldiphenylsulfoniumhexafluoroantimonate,4-(4-benzoylphenylthio)phenylbis(4-hydroxyethyloxyphenyl)sulfoniumhexafluoroantimonate,4-(4-benzoylphenylthio)phenylbis(4-fluorophenyl)sulfoniumhexafluoroantimonate,4-(4-benzoylphenylthio)phenylbis(4-chlorophenyl)sulfoniumhexafluoroantimonate,4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfoniumhexafluoroantimonate,4-(4-benzoylphenylthio)phenylbis(4-methylphenyl)sulfoniumhexafluoroantimonate,4-(4-benzoylphenylthio)phenylbis(4-hydroxyethylphenyl)sulfoniumhexafluoroantimonate,4-[4-(4-hydroxyethyloxybenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium hexafluoroantimonate,4-[4-(4-hydroxyethyloxybenzoyl)phenylthio]phenyldiphenylsulfoniumhexafluoroantimonate,4-[4-(4-hydroxyethyloxybenzoyl)phenylthio]phenylbis(4-hydroxyethyloxyphenyl)sulfoniumhexafluoroantimonate,4-(4-benzoylphenylthio)phenylbis(4-methoxyethoxyphenyl)sulfoniumhexafluoroantimonate,4-[4-(3-methoxybenzoyl)phenylthio]phenyldiphenylsulfoniumhexafluoroantimonate,4-[4-(3-methoxycarbonylbenzoyl)phenylthio]phenyldiphenylsulfoniumhexafluorantimonate,4-[4-(2-hydroxymethylbenzoyl)phenylthio]phenyldiphenylsulfoniumhexafluoroantimonate,4-[4-(4-methylbenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfoniumhexafluoroantimonate,4-[4-(4-)phenylthio]phenylbis(4-fluorophenyl)sulfoniumhexafluoroantimonate,4-[4-(4-fluorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfoniumhexafluoroantimonate,4-[4-(2-methoxycarbonylbenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium hexafluoroantimonate,bis[4-(diphenylsulfonio)phenyl]sulfide bishexafluorophosphate,bis[4-(diphenylsulfonio)phenyl]sulfide bistetrafluroborate,bis[4-(diphenylsulfonio)phenyl]sulfidetetrakis(pentafluorophenyl)borate,diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate,diphenyl-4-(phenylthio)phenylsulfonium tetrafluoroborate,diphenyl-4-(phenylthio)phenylsulfoniumtetrakis(pentafluorophenyl)borate, triphenysulfoniumhexafluorophosphate, triphenylsulfonium hexafluoroantimonate,triphenylsulfonium tetrafluoroborate, triphenylsulfoniumtetrakis(pentafluorophenyl)borate,bis[4-(di(4-2-hydroxyethoxy))phenylsulfonio)phenyl]sulfidebishexafluorophosphate,bis[4-(di(4-2-hydroxyethoxy))phenylsulfonio)phenyl]sulfidebistetrafluoroborate, andbis[4-(di(4-2-hydroxyethoxy))phenylsulfonio)phenyl]sulfidetetrakis(pentafluorophenyl)borate, and any combination thereof.

In another embodiment, the cationic photoinitiator is an aromaticiodonium salt based cationic photoinitiator selected from the groupconsisting of diphenyliodonium hexafluorophosphate, diphenyliodoniumhexafluoroantimonate, diphenyliodonium tetrafluoroborate,diphenyliodonium tetrakis(pentafluorophenyl)borate,bis(dodecylphenyl)iodonium hexafluorophosphate,bis(dodecylphenyl)iodonium hexafluoroantimonate,bis(dodecylphenyl)iodonium tetrafluoroborate, bis(dodecylphenyl)iodoniumtetrakis(pentafluorophenyl)borate,4-methylphenyl-4-(1-methylethyl)phenyliodonium hexafluorophosphate,4-methylphenyl-4-(1-methylethyl)phenyliodonium hexafluoroantimonate,4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrafluoroborate, and4-methylphenyl-4-(1-methylethyl)phenyliodoniumtetrakis(pentafluorphenyl)borate, and any combination thereof.

In certain embodiments, the cationic photoinitiator is selected from thegroup consisting of tetrakis(pentafluorophenyl)borate orhexafluoroantimonate salt of4-(4-benzoylphenylthio)phenyldiphenylsulfonium,4-(4-benzoylphenylthio)phenylbis(4-hydroxyethyloxyphenyl)sulfonium,4-(4-benzoylphenylthio)phenylbis(4-fluorophenyl)sulfonium,4-(4-benzoylphenylthio)phenylbis(4-chlorophenyl)sulfonium,4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium,4-[4-(2-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium,(4-thiophenoxyphenyl)diphenylsulfonium,S,S,S′,S′-tetraphenylthiobis(4,1-phenylene)disulfonium,triphenylsulfonium, (chlorophenyl)diphenylsulfonium,chloro[S-(phenyl)thianthrenium], S-(phenyl)thianthrenium,diphenyl-4-(4′-thiophenoxy)thiophenoxyphenylsulfonium,phenyldi(4-thiophenoxyphenyl)sulfonium,S-(4-thiophenoxyphenyl)thianthrenium, and(thiodi-4,1-phenylene)bis[bis[4-(2-hydroxyethoxy)phenyl]sulfonium,tris(4-(4-acetylphenyl)thiophenyl)sulfonium,bis(4-dodecylphenyl)iodonium,[4-[(2-hydroxytetradecyl)oxy]phenyl]phenyliodonium,(4-methylphenyl)[4-[[2-[[[[3-(trifluoromethyl)phenyl]amino]carbonyl]oxy]tetradecyl]oxy]phenyl]iodonium,bis(4-dodecylphenyl)iodonium,[4-(1-methylethyl)phenyl](4-methylphenyl)iodonium, and any combinationthereof.

In an illustrative embodiment, the liquid radiation curable resincomposition includes a cationic photoinitiator selected from the groupconsisting of triarylsulfonium SbF₆ ⁻, triarylsulfonium borate,tris(4-(4-acetylphenyl)thiophenyl)sulfoniumtetrakis(pentafluorophenyl)borate, diaryliodonium borate, iodonium[4-(1-methylethyl)phenyl](4-methylphenyl)-tetrakis(pentafluorophenyl)borate,and any combination thereof. A nonnucleophilic anion serves as thecounterion. Examples of such anions include BF₄ ³¹ , AsF₆ ⁻, SbF₆ ⁻, PF₆⁻, B(C₆F₅)₄ ⁻, perfluoroalkylsulfonates, perfluoroalkylphosphates, andcarborane anions such as (CH₆B₁₁Cl₆)⁻.

Examples of cationic photoinitiators useful for curing at 300-475 nm,particularly at 365 nm UV light, without a sensitizer include4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfoniumhexafluoroantimonate,4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfoniumtetrakis(pentafluorophenyl)borate, andtris(4-(4-acetylphenyl)thiophenyl)sulfoniumtetrakis(pentafluorophenyl)borate.

In some embodiments it is desirable for the liquid radiation curableresin composition to include a photosensitizer. The term“photosensitizer” is used to refer to any substance that eitherincreases the rate of photoinitiated polymerization or shifts thewavelength at which polymerization occurs; see textbook by G. Odian,Principles of Polymerization, 3^(rd) Ed., 1991, page 222. Examples ofphotosensitizers include those selected from the group consisting ofmethanone, xanthenones, pyrenemethanols, anthracenes, pyrene, perylene,quinones, xanthones, thioxanthones, benzoyl esters, benzophenones, andany combination thereof. Particular examples of photosensitizers includethose selected from the group consisting of[4-[(4-methylphenyl)thio]phenyl]phenyl-methanone,isopropyl-9H-thioxanthen-9-one, 1-pyrenemethanol,9-(hydroxymethyl)anthracene, 9,10-diethoxyanthracene,9,10-dimethoxyanthracene, 9,10-dipropoxyanthracene,9,10-dibutyloxyanthracene, 9-anthracenemethanol acetate,2-ethyl-9,10-dimethoxyanthracene, 2-methyl-9,10-dimethoxyanthracene,2-t-butyl-9,10-dimethoxyanthracene, 2-ethyl-9,10-diethoxyanthracene and2-methyl-9,10-diethoxyanthracene, anthracene, anthraquinones,2-methylanthraquinone, 2-ethylanthraquinone, 2-tertbutylanthraquinone,1-chloroanthraquinone, 2-amylanthraquinone, thioxanthones and xanthones,isopropyl thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone,1-chloro-4-propoxythioxanthone, methyl benzoyl formate, methyl-2-benzoylbenzoate, 4-benzoyl-4′-methyl diphenyl sulphide, 4,4′-bis(diethylamino)benzophenone, and any combination thereof.

Additionally, photosensitizers are useful in combination withphotoinitiators in effecting cure with light sources emitting in thewavelength range of 300-475 nm. Examples of suitable photosensitizersinclude: anthraquinones, such as 2-methylanthraquinone,2-ethylanthraquinone, 2-tertbutylanthraquinoe, 1-chloroanthraquinone,and 2-amylanthraquinone, thioxanthones and xanthones, such as isopropylthioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, and1-chloro-4-propoxythioxanthone, methyl benzoyl formate (Darocur MBF fromCiba), methyl-2-benzoyl benzoate (Chivacure OMB from Chitec),4-benzoyl-4′-methyl diphenyl sulphide (Chivacure BMS from Chitec),4,4′-bis(diethylamino) benzophenone (Chivacure EMK from Chitec).

In an embodiment, the photosensitizer is a fluorone, e.g.,5,7-diiodo-3-butoxy-6-fluorone, 5,7-diiodo-3-hydroxy-6-fluorone,9-cyano-5,7-diiodo-3-hydroxy-6-fluorone, or a photosensitizer is

and any combination thereof.

The liquid radiation curable resin composition can include any suitableamount of the photosensitizer, for example, in certain embodiments, inan amount up to about 10% by weight of the composition, in certainembodiments, up to about 5% by weight of the composition, and in furtherembodiments from about 0.05% to about 2% by weight of the composition.

When photosensitizers are employed, other photoinitiators absorbing atshorter wavelengths can be used. Examples of such photoinitiatorsinclude: benzophenones, such as benzophenone, 4-methyl benzophenone,2,4,6-trimethyl benzophenone, and dimethoxybenzophenone, and1-hydroxyphenyl ketones, such as 1-hydroxycyclohexyl phenyl ketone,phenyl (1-hydroxyisopropyl)ketone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, and4-isopropylphenyl(1-hydroxyisopropyl)ketone, benzil dimethyl ketal, andoligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl] propanone](Esacure KIP 150 from Lamberti). These photoinitiators when used incombination with a photosensitizer are suitable for use with lightsources emitting at wavelengths from about 100 nm to about 300 nm.

Light sources that emit visible light are also known. For light sourcesemitting light at wavelengths greater than about 400 nm, e.g., fromabout 475 nm to about 900 nm, examples of suitable photoinitiatorsinclude: camphorquinone, 4,4′-bis(diethylamino) benzophenone (ChivacureEMK from Chitec), 4,4′-(bis(N,N′-dimethylamino) benzophenone (Michler'sketone), bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (Irgacure 819or BAPO from Ciba), metallocenes such as bis(eta5-2-4-cyclopentadien-1-yl) bis[2,6-difluoro-3-(1H-pyrrol-1-yl) phenyl]titanium (Irgacure 784 from Ciba), and the visible light photoinitiatorsfrom Spectra Group Limited, Inc. such as H-Nu 470, H-Nu-535, H-Nu-635,H-Nu-Blue-640, and H-Nu-Blue-660.

A photosensitizer or co-initiator may be used to improve the activity ofthe cationic photoinitiator. It is for either increasing the rate ofphotoinitiated polymerization or shifting the wavelength at whichpolymerization occurs. The sensitizer used in combination with theabove-mentioned cationic photoinitiator is not particularly limited. Avariety of compounds can be used as photosensitizers, includingheterocyclic and fused-ring aromatic hydrocarbons, organic dyes, andaromatic ketones. Examples of sensitizers include compounds disclosed byJ. V. Crivello in Advances in Polymer Science, 62, 1 (1984), and by J.V. Crivello & K. Dietliker, “Photoinitiators for CationicPolymerization” in Chemistry & technology of UV & EB formulation forcoatings, inks & paints. Volume III, Photoinitiators for free radicaland cationic polymerization, by K. Dietliker; [Ed. by P. K. T. Oldring],SITA Technology Ltd, London, 1991. Specific examples includepolyaromatic hydrocarbons and their derivatives such as anthracene,pyrene, perylene and their derivatives, thioxanthones,α-hydroxyalkylphenones, 4-benzoyl-4′-methyldiphenyl sulfide, acridineorange, and benzoflavin.

There are a large number of known and technically proven cationicphotoinitiators that are suitable. They include, for example, oniumsalts with anions of weak nucleophilicity. Examples are halonium salts,iodosyl salts or sulfonium salts, such as are described in publishedEuropean patent application EP 153904 and WO 98/28663, sulfoxoniumsalts, such as described, for example, in published European patentapplications EP 35969, 44274, 54509, and 164314, or diazonium salts,such as described, for example, in U.S. Pat. Nos. 3,708,296 and5,002,856. All eight of these disclosures are hereby incorporated intheir entirety by reference. Other cationic photoinitiators aremetallocene salts, such as described, for example, in published Europeanapplications EP 94914 and 94915, which are both hereby incorporated intheir entirety by reference.

A survey of other current onium salt initiators and/or metallocene saltscan be found in “UV Curing, Science and Technology”, (Editor S. P.Pappas, Technology Marketing Corp., 642 Westover Road, Stamford, Conn.,(U.S.A.) or “Chemistry & Technology of UV & EB Formulation for Coatings,Inks & Paints”, Vol. 3 (edited by P. K. T. Oldring).

Suitable ferrocene type cationic photoinitiators include, for example,di(cyclopentadienyliron)arene salt compounds of formula (I) as disclosedin Chinese Patent No. CN 101190931:

wherein anion MXn is selected from BF4, PF6, SbF6, AsF6, (C6F5)4B, ClO4,CF3SO3, FSO3, CH3SO3, C4F9SO3, and Ar is a fused ring or polycyclicarene.

Other illustrative ferrocene type cationic photoinitiators include, forexample, (Θ6-Carbazole) (η5-cyclopenta-dienyl) iron hexafluorophosphatesalts, specifically [cyclopentadiene-Fe—N-butylcarbazole]hexafluoro-phosphate (C4-CFS PF6) and[cyclopentadiene-Fe—N-octyl-carbazole] hexafluorophosphate (C8-CFS PF6),bearing C4 and C8 alkyl chains, respectively, on the nitrogen atom (seePolymer Eng. & Science (2009), 49(3), 613-618); ferrocenium dicationsalts, e.g., biphenyl bis[(π-cyclopentadienyl) iron] hexafluorophosphate([bis(Cp-Fe)-biphenyl] (PF6)2) and straight cyclopentadien-iron-biphenylhexafluorophosphate ([Cp-Fe-biphenyl]+PF6−) as disclosed in Chinese J.Chem. Engnrng (2008), 16(5), 819-822 and Polymer Bulltn (2005), 53(5-6),323-331; cyclopentadienyl-Fe-carbazole hexafluorophosphate([Cp-Fe-carbazole]+PF6-), cyclopentadienyl-Fe—N-ethylcarbazolehexafluorophosphate ([Cp-Fe-n-ethylcarbazole]+PF6-) andcyclopentadienyl-Fe-aminonaphthalene hexafluorophosphate([Cp-Fe-aminonaphthalene]+PF6-) as disclosed in J Photochem. &Photobiology, A: Chemistry (2007), 187(2-3), 389-394 and Polymer Intnl(2005), 54(9), 1251-1255; alkoxy-substituted ferrocenium salts, forexample, [cyclopendadien-Fe-anisole]PF6, [cyclopendadien-Fe-anisole]BF4,[cyclopendadien-Fe-diphenylether]PF6,[cyclo-pendadien-Fe-diphenylether]BF4, and[cyclopendadien-Fe-diethoxy-benzene]PF6, as disclosed in Chinese J. ofChem Engnrng (2006), 14(6), 806-809; cyclopentadiene-iron-arenetetrafluoroborates, for example, cyclopentadiene-iron-naphthalenetetrafluoroborate ([Cp-Fe-Naph] BF4) salt, as disclosed in ImagingScience J (2003), 51(4), 247-253; ferrocenyl tetrafluoroborate([Cp-Fe-CP]BF4), as disclosed in Ganguang Kexue Yu Guang Huaxue (2003),21(1), 46-52; [CpFe(η6-tol)]BF4, as disclosed in Ganguang Kexue Yu GuangHuaxue (2002), 20(3), 177-184, Ferrocenium salts (η6-α-naphthoxybenzene)(η5-cyclopentadienyl) iron hexafluorophosphate (NOFC-1) and(η6-β-naphthoxybenzene) (η5-cyclopentadienyl) iron hexafluorophosphate(NOFC-2), as disclosed in Int. J of Photoenergy (2009), Article ID981065; (η6-Diphenyl-methane) (η5-cyclopentadienyl) ironhexafluorophosphate and (η6-benzophenone) (η5-cyclopenta-dienyl) ironhexafluorophosphate, as disclosed in Progress in Organic Coatings(2009), 65(2), 251-256; [CpFe(η6-isopropyl-benzene)]PF6, as disclosed inChem Comm (1999), (17), 1631-1632; and any combination thereof.

Suitable onium type cationic photoinitiators include, for example,iodonium and sulfonium salts, as disclosed in Japanese Patent JP2006151852. Other illustrative onium type photoinitiators include, forexample, onium salts such as, diaryliodonium salts, diaryl-iodoxoniumsalts, triaryl-sulfoxonium salts, dialkylphenacyl-sulfonium salts,dialkylhydroxy-phenysulfonium salts, phenacyl-triarylphosphonium salts,and phenacyl salts of heterocyclic nitrogen-containing compounds, asdisclosed in U.S. Pat. No. 5,639,413; 5,705,116; 5,494,618; 6,593,388;and Chemistry of Materials (2002), 14(11), 4858-4866; aromatic sulfoniumor iodonium salts as disclosed in U.S. Patent Application No.2008/0292993; diaryl-, triaryl-, or dialkylphenacylsulfonium salts, asdisclosed in US2008260960 and J. Poly Sci. Part A (2005), 43(21), 5217;diphenyl-iodonium hexafluorophosphate (Ph21+PF6-), as disclosed inMacromolecules (2008), 41(10), 3468-3471; onium salts using onium saltsusing less toxic anions to replace, e.g., SbF6-. Mentioned are anions:B(C6F5)4-, Ga(C6F5)4- and perfluoroalkyl fluorophosphate, PfnRf(6−n)-,as disclosed in Nettowaku Porima (2007), 28(3), 101-108; Photoactiveallyl ammonium salt (BPEA) containing benzophenone moiety in thestructure, as disclosed in Eur Polymer J (2002), 38(9), 1845-1850;1-(4-Hydroxy-3-methylphenyl) tetrahydrothiophenium hexafluoroantimonate,as disclosed in Polymer (1997), 38(7), 1719-1723; and any combinationthereof.

Illustrative iodonium type cationic photoinitiators include, forexample, diaryliodonium salts having counterions likehexafluoro-phosphate and the like, such as, for example,(4-n-pentadecyloxy-phenyl)phenyliodonium hexa-fluoroantimonate, asdisclosed in US2006041032; diphenyliodonium hexafluorophosphate, asdisclosed in U.S. Pat. No. 4,394,403 and Macromolecules (2008), 41(2),295-297; diphenyliodonium ions as disclosed in Polymer (1993), 34(2),426-8; Diphenyliodonium salt with boron tetrafluoride (Ph2I+BF4-), asdisclosed in Yingyong Huaxue (1990), 7(3), 54-56; SR-1012, adiaryldiodonium salt, as disclosed in Nuclear Inst. & Methods in PhysicsRes. B (2007), 264(2), 318-322; diaryliodonium salts, e.g.,4,4′-di-tert-butyldiphenyl-iodonium hexafluoroarsenate, as disclosed inJ Polymr Sci, Polymr Chem Edition (1978), 16(10), 2441-2451;Diaryliodonium salts containing complex metal halide anions such asdiphenyliodonium fluoroborate, as disclosed in J Polymr Sci, Poly Sympos(1976), 56, 383-95; and any combination thereof.

Illustrative sulfonium type cationic type photoinitiators include, forexample, UVI 6992 (sulfonium salt) as disclosed in Japanese patentJP2007126612; compounds of the formula:

where R1-2=F; R3=isopropyl; R4=H; X=PF6, as disclosed in Japanese patentJP10101718; thioxanthone-based sulfonium salts, e.g., of the formula:

as disclosed in U.S. Pat. No. 6,054,501; (Acyloxyphenyl)sulfonium saltsof the type R₃-xS+R3x A-, where A- is a non-nucleophilic anion such asAsF₆-, and R3 may be the phenyl group shown below:

as disclosed in U.S. Pat. No. 5,159,088; 9,10-dithiophenoxyanthracenealkyldiarylsulfonium salts, e.g.,ethylphenyl(9-thiophenoxy-anthracentyl-10) sulfoniumhexafluoroantimonate, and the like, as disclosed in U.S. Pat. No.4,760,013; etc.; triphenylsulfonium hexafluorophosphate salt, asdisclosed in U.S. Pat. No. 4,245,029;S,S-dimethyl-S-(3,5-dimethyl-2-hydroxyphenyl)sulfonium salts, asdisclosed in J Poly Sci, Part A (2003), 41(16), 2570-2587;Anthracene-bound sulfonium salts, as disclosed in J Photochem &Photobiology, A: Chemistry (2003), 159(2), 161-171; triarylsulfoniumsalts, as disclosed in J Photopolymer Science & Tech (2000), 13(1),117-118 and J Poly Science, Part A (2008), 46(11), 3820-29;S-aryl-S,S-cycloalkylsulfonium salts, as disclosed in J Macromol Sci,Part A (2006), 43(9), 1339-1353; dialkylphenacylsulfonium salts, asdisclosed in UV & EB Tech Expo & Conf, May 2-5, 2004, 55-69 and ACS SympSer (2003), 847, 219-230; Dialkyl(4-hydroxyphenyl)sulfonium salts, andtheir isomeric dialkyl(2-hydroxyphenyl)sulfonium salts, as disclosed inACS 224th Natnl Meeting, Aug. 18-22, 2002, POLY-726;Dodecyl(4-hydroxy-3,5-dimethylphenyl)methylsulfonium hexafluorophosphateand similar alkyl analogs other than dodecyl.Tetrahydro-1-(4-hydroxy-3,5-dimethylphenyl)thiopheniumhexafluorophosphate andtetrahydro-1-(2-hydroxy-3,5-dimethylphenyl)thiopheniumhexafluorophosphate, as disclosed in ACS Polymer Preprints (2002),43(2), 918-919; photoinitiators with the general structureAr'S+CH3(Cl2H25)SbF6-, where Ar' is phenacyl (I), 2-indanonyl (II),4-methoxyphenacyl (III), 2-naphthoylmethyl (IV), 1-anthroylmethyl (V),or 1-pyrenoylmethyl (VI), as disclosed in J Polymr Sci, Part A (2000),38(9), 1433-1442; Triarylsulfonium salts Ar3S+MXn- with complex metalhalide anions such as BF4-, AsF6-, PF6-, and SBF6-, as disclosed in JPolymr Sci, Part A (1996), 34(16), 3231-3253; Dialkylphenacylsulfoniumand dialkyl(4-hydroxyphenyl) sulfonium salts, as disclosed inMacromolecules (1981), 14(5), 1141-1147; Triarylsulfonium saltsR2R1S+MFn- R, R1=Ph or substituted phenyl; M=B, As, P; n=4 or 6) and thesulfonium salt of formula (I):

as disclosed in J. Polymr. Sci, Polymr Chem Edition (1979), 17(4),977-99; aromatic sulfonium salts with, e.g., PF6- anion, e.g., UVI 6970,as disclosed in JP 2000239648; and any combination thereof.

Suitable pyridinium type cationic photoinitiators include, for example,N-ethoxy 2-methylpyridinium hexafluorophosphate (EMP+PF6-), as disclosedin Turkish J of Chemistry (1993), 17(1), 44-49; Charge-transfercomplexes of pyridinium salts and aromatic electron donors(hexamethyl-benzene and 1,2,4-trimethoxy-benzene), as disclosed inPolymer (1994), 35(11), 2428-31; N,N′-diethoxy-4,4′-azobis(pyridinium)hexafluorophosphate (DEAP), as disclosed in Macromolecular Rapid Comm(2008), 29(11), 892-896; and any combination thereof.

Other suitable cationic photoinitiators include, for example,Acylgermane based photoinitiator in the presence of onium salts, e.g.,benzoyltrimethylgermane (BTG) and onium salts, such as diphenyl-iodoniumhexafluorophosphate (Ph2I+PF6-) or N-ethoxy-2-methyl-pyridiniumhexafluorophosphate (EMP+PF6-), as disclosed in Macromolecules (2008),41(18), 6714-6718; Di-Ph diselenide (DPDS), as disclosed inMacromolecular Symposia (2006), 240, 186-193;N-phenacyl-N,N-dimethyl-anilinium hexafluoroantimonate (PDA+SbF6-), asdisclosed in Macromol Rapid Comm (2002), 23(9), 567-570; Synergisticblends of: diaryliodonium hexafluoro-antimonate (IA) withtolylcumyl-iodonium tetrakis(pentafluoro-phenyl)borate (IB), andcumenecyclopentadienyliron(II) hexafluorophosphate with IA and IB, asdisclosed in Designed Monomers and Polymers (2007), 10(4), 327-345;Diazonium salts, e.g., 4-(hexyloxy)-substituted diazonium salts withcomplex anions, as disclosed in ACS Symp Series (2003), 847, 202-212;5-Arylthianthrenium salts, as disclosed in J Poly Sci, Part A (2002),40(20), 3465-3480; and any combination thereof.

Other suitable cationic photoinitiators include, for example,triarylsulfonium salts such as triarylsulfonium borates modified forabsorbing long wavelength UV. Illustrative examples of such modifiedborates include, for example, SP-300 available from Denka,tris(4-(4-acetylphenyl)thiophenyl)sulfoniumtetrakis(pentafluorophenyl)borate (GSID4480-1 or Irgacure PAG-290)available from Ciba/BASF, and those photoinitiators disclosed inWO1999028295; WO2004029037; WO2009057600; U.S. Pat. No. 6,368,769WO2009047105; SO2009047151; WO2009047152; U.S. 20090208872; and U.S.Pat. No. 7,611,817.

Preferred cationic photoinitiators include a mixture of:bis[4-diphenylsulfoniumphenyl]sulfide bishexafluoroantimonate;thiophenoxyphenylsulfonium hexafluoroantimonate (available as Chivacure1176 from Chitec); tris(4-(4-acetylphenyl)thiophenyl)sulfoniumtetrakis(pentafluorophenyl)borate (GSID4480-1 from Ciba/BASF), iodonium,[4-(1-methylethyl)phenyl](4-methylphenyl)-,tetrakis(pentafluorophenyl)borate (available as Rhodorsil 2074 fromRhodia),4-[4-(2-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfoniumhexafluoroantimonate (as SP-172) and SP-300 (both available from Adeka).

The liquid radiation curable resin composition can include any suitableamount of the cationic photoinitiator, for example, in certainembodiments, in an amount an amount up to about 50% by weight of thecomposition, in certain embodiments, up to about 20% by weight of thecomposition, and in further embodiments from about 1% to about 10% byweight of the composition. In a further embodiment, the amount ofcationic photoinitiator is from about 0.25 wt % to about 8 wt % of thetotal composition, more preferably from about 1 wt % to about 6 wt %. Inan embodiment, the above ranges are particularly suitable for use withepoxy monomers.

In accordance with an embodiment, the liquid radiation curable resincomposition can further include a chain transfer agent, particularly achain transfer agent for a cationic monomer. The chain transfer agenthas a functional group containing active hydrogen. Examples of theactive hydrogen-containing functional group include an amino group, anamide group, a hydroxyl group, a sulfo group, and a thiol group. In anembodiment, the chain transfer agent terminates the propagation of onetype of polymerization, i.e., either cationic polymerization orfree-radical polymerization and initiates a difference type ofpolymerization, i.e., either free-radical polymerization or cationicpolymerization. In accordance with an embodiment, chain transfer to adifferent monomer is a preferred mechanism. In embodiments, chaintransfer tends to produce branched molecules or crosslinked molecules.Thus, chain transfer offers a way of controlling the molecular weightdistribution, crosslink density, thermal properties, and/or mechanicalproperties of the cured resin composition.

Any suitable chain transfer agent can be employed. For example, thechain transfer agent for a cationic polymerizable component is ahydroxyl-containing compound, such as a compound containing 2 or morethan 2 hydroxyl-groups. In an embodiment, the chain transfer agent isselected from the group consisting of a polyether polyol, polyesterpolyol, polycarbonate polyol, ethoxylated or propoxylated aliphatic oraromatic compounds having hydroxyl groups, dendritic polyols,hyperbranched polyols. An example of a polyether polyol is a polyetherpolyol comprising an alkoxy ether group of the formula [(CH2)_(n)O]_(m),wherein n can be 1 to 6 and m can be 1 to 100.

A particular example of a chain transfer agent is polytetrahydrofuransuch as TERATHANE™.

The liquid radiation curable resin composition can include any suitableamount of the chain transfer agent, for example, in certain embodiments,in an amount up to about 50% by weight of the composition, in certainembodiments, up to about 30% by weight of the composition, and incertain other embodiments from about 10% to about 20% by weight of thecomposition.

The liquid radiation curable resin composition of the invention canfurther include one or more additives selected from the group consistingof bubble breakers, antioxidants, surfactants, acid scavengers,pigments, dyes, thickeners, flame retardants, silane coupling agents,ultraviolet absorbers, resin particles, core-shell particle impactmodifiers, soluble polymers and block polymers, organic, inorganic, ororganic-inorganic hybrid fillers of sizes ranging from 8 nanometers toabout 50 microns.

Stabilizers are often added to the compositions in order to prevent aviscosity build-up, for instance a viscosity build-up during usage in asolid imaging process. In an embodiment, stabilizers include thosedescribed in U.S. Pat. No. 5,665,792, the entire disclosure of which ishereby incorporated by reference. Such stabilizers are usuallyhydrocarbon carboxylic acid salts of group IA and IIA metals. In otherembodiments, these salts are sodium bicarbonate, potassium bicarbonate,and rubidium carbonate. Rubidium carbonate is preferred for formulationsof this invention with recommended amounts varying between 0.0015 to0.005% by weight of composition. Alternative stabilizers includepolyvinylpyrrolidones and polyacrylonitriles. Other possible additivesinclude dyes, pigments, fillers (e.g. silica-particles—preferablycylindrical or spherical silica particles—, talc, glass powder, alumina,alumina hydrate, magnesium oxide, magnesium hydroxide, barium sulfate,calcium sulfate, calcium carbonate, magnesium carbonate, silicatemineral, diatomaceous earth, silica sand, silica powder, titanium oxide,aluminum powder, bronze powder, zinc powder, copper powder, lead powder,gold powder, silver dust, glass fiber, titanic acid potassium whisker,carbon whisker, sapphire whisker, beryllia whisker, boron carbidewhisker, silicon carbide whisker, silicon nitride whisker, glass beads,hollow glass beads, metaloxides and potassium titanate whisker),antioxidants, wetting agents, photosensitizers for the free-radicalphotoinitiator, chain transfer agents, leveling agents, defoamers,surfactants and the like.

In accordance with an embodiment of the invention, the liquid radiationcurable resin composition contains the polymerizable components suchthat the desired photosensitivity is obtained by choosing an appropriateratio of the initiators and/or polymerizable components. The ratio ofthe components and of the initiators affect the photosensitivity, speedof curing, degree of curing, crosslink density, thermal properties(e.g., T_(g)), and/or mechanical properties (e.g., tensile strength,storage modulus, loss modulus) of the liquid radiation curable resincomposition or of the cured article.

Accordingly, in an embodiment, the ratio by weight of cationicphotoinitiator to free-radical photoinitiator (CPI/RPI) is less thanabout 4.0, preferably from about 0.1 to about 2.0, and more preferablyfrom about 0.2 to about 1.0.

In accordance with an embodiment, the liquid radiation curable resincomposition has a ratio by weight of cationic polymerizable component tofree-radical polymerizable component (CPC/RPC) is less than about 7.0,or less than about 5.0, e.g., from about 0.5 to about 2.0, and morepreferably from about 1.0 to about 1.5.

The second aspect of the instant claimed invention is athree-dimensional article having at least one selectively colored and/ortransparent region made using an additive fabrication process, wherein aliquid radiation curable resin used to create the article comprises fromabout 0.005 wt % to about 5 wt % of at least one thermally sensitivevisual effect initiator.

The third aspect of the instant claimed invention is a liquid radiationcurable resin wherein the liquid radiation curable resin compositioncomprises at least two thermally sensitive visual effect initiators.

By incorporating more than one thermally sensitive visual effectinitiator into the liquid radiation curable resin, different levels ofcolor and/or transparency can be achieved. In an embodiment, more thanone thermally sensitive visual effect initiator can be incorporated intothe liquid radiation curable resin wherein the more than one thermallysensitive visual effect initiators all have the same activation andlocking temperatures in order to obtain unique combinations of colorand/or transparency.

By incorporating more than one thermally sensitive visual effectinitiator into the liquid radiation curable resin, wherein eachthermally sensitive visual effect initiator has a different temperaturerequirement for activation, a three-dimensional article can havemultiple colors or transparencies by selectively varying the localtemperature during cure. For instance, an article having three differentcolors, transparencies, or some combination, would have two thermallysensitive visual effect initiators and be exposed to three differentlocal temperatures during cure, for instance by irradiation with threedifferent doses of light. A first dose would be used to cure the articlewithout activating either component. A second dose, higher than thefirst dose, would be used to activate one of the thermally sensitivevisual effect initiators in the areas exposed to the second dose oflight. A third dose, higher than the first dose and the second dose,would activate both thermally sensitive visual effect initiators in theareas exposed to the third dose of light, thus producing an articlepossessing multiple different colors and/or transparency levels in someareas and optionally clear and substantially colorless in other areas.The amount of thermally sensitive visual effect initiators added to aliquid radiation curable resin and the amount of different doses oflight used to irradiate the liquid radiation curable resin have no limitas long as the temperature of the resin can be appropriately controlled.

The fourth aspect of the instant claimed invention is a method offorming a three-dimensional article having regions of selective colorand/or transparency from a liquid radiation curable resin comprising thesteps:

curing a layer of a liquid radiation curable resin using light, therebyforming a cured solid polymeric layer;

irradiating selected areas of the cured solid polymeric layer resultingfrom step (a), a previously cured solid polymeric layer, or a layer ofthe liquid radiation curable resin with a higher dose of light than usedin step (a) thereby removing color and/or altering the transparency ofthe areas irradiated with the higher dose of light.

repeating steps (a) and (b) on a previously cured solid polymeric layeror a layer of the liquid radiation curable resin, as necessary, untilthe desired three-dimensional article having selectively colored and/ortransparent regions is formed;

wherein the wavelength(s) of light in each of steps (a) and (b) are thesame, and step (b) can be performed before, during, or after step (a).

In this method, the resin has a first level of color and/or transparencyafter performance of step (a), and has a different level of color and/ortransparency after performance of step (b). Steps (a) and (b) can beperformed in either order or simultaneously. The number of times thatsteps (a) and (b) can be repeated according to step (c) depends on thethickness of the polymeric layers and the size of the three-dimensionalarticle being created. The polymeric layers do not need to all be of thesame depth or thickness.

When step (b) is performed, the color and/or transparency of the areasilluminated with light is altered, thus forming a selectively coloredand/or transparent article. It is possible to omit step (b) on certainlayers in order to not alter the color and/or transparency of anysection of that layer. It is also possible to omit step (a) on certainlayers in order to only alter the color and/or transparency in anysection of that layer.

The dose of light used in step (b) is higher than the dose of light usedin step (a). In an embodiment, the dose of light used in step (b) is atleast two times the dose used in step (a). The higher dose of light canbe achieved by, for example, increasing the length of time that thelight illuminates the layer of the composition. The higher dose of lightcan also be achieved by increasing the intensity of the light used toilluminate the layer of the composition. Those skilled in the art ofthree-dimensional article production by additive fabrication understandhow to adjust the machine to change the intensity of the light sourceand to irradiate a layer with a higher dose of light.

In an embodiment, only a single dose of light is used to cure a liquidradiation curable resin comprising at least one thermally sensitivevisual effect initiator thereby altering the color and/or thetransparency from all of the liquid radiation curable resin or none ofthe liquid radiation curable resin. Additional steps can be added to thefourth aspect of the instant claimed invention such that lights ofhigher doses can be used in order to activate additional thermallysensitive visual effect initiators.

The wavelength of the light used to cure the liquid radiation curableresin is preferably greater than about 100 nm and less than about 900nm. More preferably, the wavelength of the light is between about 200 nmand about 700 nm. More preferably, the wavelength of the light isbetween about 250 nm and to about 450 nm, more preferably between 300and 415 nm.

In an embodiment, the liquid radiation curable resin used in the fourthaspect of the instant claimed invention comprises at least one thermallysensitive visual effect initiator. In another embodiment, the liquidradiation curable resin used in the fourth aspect of the instant claimedinvention comprises at least one thermochromic component. In anembodiment, the liquid radiation curable resin used in the fourth aspectof the instant claimed invention comprises at least one thermallysensitive transparency modifier.

In another embodiment, the additional step of overexposing a cured solidpolymeric layer formed in step (b) or step (c) is performed.Overexposing the cured solid polymeric layer causes the layer to besomewhat burned and will allow further change in the color or shade ofthe cured solid polymeric layer. Those skilled in additive fabricationmachine operation know how to overexpose a cured solid polymeric layerin order to manipulate the shade or color of the cured solid polymericlayer.

In some embodiments, the light source used to cure the liquid radiationcurable resin is a laser such as a He—Cd laser or an Argon ion laser.Such lasers are common on commercially available stereolithographymachines and known in the art. In other embodiments, the light source isa light-emitting diode (LED). In other embodiments, the light source isa lamp. In still further embodiments, the light is delivered to theliquid radiation curable resin using an image produced from a DMD(digital micromirror device) chip or LCD display. At least twointensities can be created by a single light source or by multiple lightsources. In an embodiment, a single light source is used. In anotherembodiment, a second light source is used in combination with the firstlight source to increase the light intensity delivered to certain areasof the radiation curable resin.

It is possible that the color or transparency change will beinsufficient in some areas of the cured three-dimensional article afterpolymerization. This occurrence is most likely at the edges of the partwhere it is more difficult to locally control the temperature duringcuring. In order to alter the color and/or transparency after curing ofthe liquid radiation curable resin, the cured three-dimensional articlecan be locally heated in those areas. Such local heating can beaccomplished with any heat source that can provide local heat, such as aheat gun or small torch.

The fifth aspect of the instant claimed invention is a method of forminga three-dimensional article having selectively colored and/ortransparent regions made from a liquid radiation curable resin whereinthe coloration and/or transparency of the selectively colored and/ortransparent regions is created by selectively controlling thetemperature of the liquid radiation curable resin.

In an embodiment, the liquid radiation curable resin used in the fifthaspect of the instant claimed invention comprises at least one thermallysensitive visual effect initiator. In another embodiment, the liquidradiation curable resin used in the fifth aspect of the instant claimedinvention comprises at least one thermochromic component. In anembodiment, the liquid radiation curable resin used in the fifth aspectof the instant claimed invention comprises at least one thermallysensitive transparency modifier.

The sixth aspect of the instant claimed invention is a three-dimensionalarticle having colored and uncolored section produced via an additivefabrication process that when exposed to fluorescent light for 30 daysat ambient temperature attains a ΔE* measured throughout the exposure tofluorescent light that remains within 50% of the ΔE* measured on thefirst day of the exposure to fluorescent light, preferably the ΔE*measured through the exposure to fluorescent light remains within 30% ofthe ΔE* measured on the first day of the exposure to fluorescent light,more preferably the ΔE* measured through the exposure to fluorescentlight remains within 15% of the ΔE* measured on the first day of theexposure to fluorescent light, even more preferably the ΔE* measuredthrough the exposure of fluorescent light remains within 10% of the ΔE*measured on the first day of the exposure to fluorescent light.

The seventh aspect of the instant claimed invention is a method offorming a three-dimensional article having selectively colored and/ortransparent regions from a liquid radiation curable resin comprising thesteps of

-   -   a. selectively curing a layer of liquid radiation curable resin        with at least two different doses of light thereby forming a        cured solid layer with selectively colored and/or transparent        regions    -   b. juxtaposing at least two cured solid layers formed from        step (a) in order to form a three-dimensional article.

The eight aspect of the instant claimed invention is a liquid radiationcurable resin composition capable of curing into a solid uponirradiation comprising from 0.005 wt % to 5 wt % of at least onethermally sensitive visual effect initiator, preferably from 0.005 wt %to 3 wt. %, more preferably from 0.005 wt % to 2.5 wt. %, even morepreferably from 0.005 wt % to 1 wt %, even more preferably from 0.005 wt% to 0.5 wt %, of the at least one thermally sensitive visual effectinitiator.

The following examples further illustrate the invention but, of course,should not be construed as in any way limiting its scope.

EXAMPLES

Some example compositions are made by adding 0.3 wt % of Thermolock® 79sPink to Clear to commercially available SOMOS® WaterClear® Ultra 10122liquid radiation curable resin and then mixed in a mixer forapproximately 15 minutes until combined. Additional comparative examplecompositions are made using the commercially available Renshape® SL Y-C9300 liquid radiation curable resin, available from Huntsman AdvancedMaterials, without adding any other components. All three-dimensionalarticles were not coated with any protective clear coat for these tests.

Rectangular parts of size 3.0 in×0.25 in×1.5 in (7.62 cm×0.635 cm×3.81cm) are created. One half of this part (1.5 in×0.25 in×1.5 in or 3.81cm×0.635 cm×3.81 cm) is selected to be colored while the other half isselected to have no color. These parts are built using a Coherent AVIA355-1800 Solid State Laser. The spot diameter is 0.0277 cm in they-direction and 0.0245 cm in the x-direction. The frequency is set to 80kHz giving a laser power of 91 mW at the part. The stereolithographymachine used is an experimental Solid State Imaging machine built byDuPont in 1990. Parts are designed and built using Soliform software.The parts are built using a 0.007 inch (0.1778 mm) slice layer, 3 milengagement, 0.001 inch scan spacing, varying the line width (whichvaries the scan speed) to change the exposure each part receives. Pinkparts are created using a 68 linewidth (corresponding to a 725.6 cm/secscan speed). Parts having no color are created when the linewidth iseither a 144 linewidth (437.2 cm/sec scan speed) or a 184 linewidth(343.2 cm/sec scan speed). A 40 seconds dip wait time is used betweenlayers to dissipate heat. The temperature of the resin in this machinecan be controlled by external heaters. The parts were made with a resinvat temperature of 32+/−4° C. The parts are cleaned using isopropanol.

Comparatively example parts of similar dimensions are created usingcommercially available Renshape® SL Y-C 9300 material, available fromHuntsman Advanced Materials. These parts are built on a SLA-5000machine. No clear coat is added to the Renshape® SL Y-C 9300 parts.These parts show a great deal of sag and curl. In order to obtain theproper shape, the parts are wet sanded with 600 grit sand paper,followed by a 1000 grit, then 2000 grit paper sanding. The sanding isfollowed by a Novis 1 buffing wheel. The example compositions in wt %are shown below in Table 1. CE is meant to signify a comparative examplethat is not to be construed as an example of the invention.

TABLE 1 Component Somos ® Thermolock ® WaterClear 79s Pink to Renshape ®Line Example Ultra 10122 Clear SLY-C 9300 Width 1 99.7 0.3 0 184 2 99.70.3 0 184 3 99.7 0.3 0 184 4 99.7 0.3 0 144 5 99.7 0.3 0 144 6 99.7 0.30 144 CE1 0 0 100 CE2 0 0 100 CE3 0 0 100

Transmittance, Haze, and Clarity

Transmittance, Haze, and Clarity measurements are taken using aBYK-Gardner haze-gard plus (0° diffuse geometry using an illuminant C)on several samples. Transmittance is the ratio of transmitted light tothe incident light; it is influenced by the absorption and reflectionproperties of the sample. Haze is defined by ASTM D 1003 as thatpercentage of light which in passing through deviates from the incidentbeam greater than 2.5 degrees on average. Clarity is the narrow anglescattered light. Additional information on the measurement equipment andmethodology can be found in QC Solutions for Coatings and Plastics2005-2006,© 2004 BYK-Gardner Instruments, incorporated herein byreference. The test results are shown in Table 2. Each reported valuefor transmission, haze, or clarity, is the result of the average of fivereading taken from five randomly selected areas of the sample. The idealresult for the clear section is a low haze value and a high clarityvalue. The ideal result for the colored section is a high haze value anda low clarity value.

TABLE 2 Clear Pink Average St. Dev. Average St. Dev. Example 1 Trans82.4 0.06 48.1 0.26 Haze 23.4 1.07 63.4 3.34 Clarity 92.6 1.23 73.2 3.62Example 2 Trans 82.3 0.06 44.1 0.71 Haze 25.4 0.9 93.4 1.5 Clarity 84.45.39 25.4 5.12 Example 3 Trans 82.6 0.1 49.2 0.17 Haze 22.5 0.87 63.30.95 Clarity 93.5 1.77 79.3 6.29 Example 4 Trans 81.6 0 46.8 0 Haze 35.80.79 69 0.66 Clarity 93.7 0.38 86.4 0.15 Example 5 Trans 80.4 0.67 46.20.53 Haze 52.6 4.96 81.7 5.48 Clarity 86.3 0.7 53.2 8.98 Example 6 Trans80.7 0.36 43.14 0.76 Haze 47 1.2 95.0 0.87 Clarity 91.4 1.08 4.8 0.36Comparative Trans 88 0.21 16 0.19 Example 1 Haze 92.3 0.38 31.5 0.6Clarity 5.46 0.43 78.6 1.79 Comparative Trans 88.3 0.38 16.6 0.07Example 2 Haze 95.5 0.49 27.9 0.57 Clarity 4.28 0.2 74.8 0.6 ComparativeTrans 88.4 0.07 16.3 0.32 Example 3 Haze 91.9 0.42 29.8 1.01 Clarity7.64 0.44 67.4 5.05

Color Stability

Measurement of color can be performed with a Chroma meter. A Chromameter can be used to measure either an opaque article or resin, or atransparent or translucent article or resin. When the article or resinis opaque, the color of the article or resin can be used by directlymeasuring the color with the Chroma meter. However, if the article orresin is transparent or translucent, the color measurement is performedagainst a white barium sulfate tile background.

The International Commission of Illumination (CIE) publishes therecognized standard on perception of color. The standards can bepurchased from the CIE website athttp://www.cie.co.at/index.php/Publications/Standards. The CIE alsopublishes recognized standards on illumination sources such as standardilluminants D65 and Illuminant C. D65 is used to simulate standardaverage daylight, including UV wavelength light. Illuminant C is used tosimulate daylight without UV wavelength light. A Chroma meter willmeasure three values, ‘L’, ‘a’, and ‘b’. L is the lightness. Thelightness (L) will be 100 for white materials and 0 for totally blackmaterials. The ‘a’ and ‘b’ values are used to measure actual color. The‘a’ and ‘b’ values are measured on a scale of −60 to +60. The ‘−a’ valuerepresents green, the ‘+a’ value represents red, the ‘−b’ valuerepresents blue and the ‘+b’ value represents yellow. Parts having ‘a’and ‘b’ values between −20 and 20 will have a rather gray appearance.Parts having ‘a’ or ‘b’ values between −20 and −60 or 20 and 60 will bemore colorful.

Color stability is measured using a Macbeth Model 7000 Color EyeColorimeter, a chroma meter. The Macbeth Model 7000 Color EyeColorimeter is used to measure color inclusively in CIE L*a*b* colorspace (Illuminant D65-10° deg. Observer). Color readings are measuredevery 2 to 3 days for a one month period. The change in contrast betweenthe color and uncolored portions of the samples is measured bycalculating the total change in color, ΔE*, between the clear half andthe colored half. ΔE* is calculated by √{square root over(ΔL²+Δa²+Δb²)}. Three conditions are tested. In the control condition,the samples are wrapped in a cloth and placed inside a dark bag inside adark desk drawer. In the fluorescent light condition, the samples areplaced under a standard 25 Watt fluorescent office light (Trimline T8F25T8 SP35). In the natural light condition, the samples are placed onan East-facing windowsill. The change in the samples'color and contrastover time is recorded. Table 3 represents the control condition, Table 4represents the fluorescent light condition, and Table 5 represents thenatural light condition.

FIG. 5 shows three-dimensional articles made from the composition asused in Example 1, 2, and 3 cured with a line width of 184 in theuncolored regions and 68 in the colored regions (184/68) in comparisonto the current state of the art Renshape® SL Y-C 9300. The articles onthe top of FIG. 5 (top-left and top-right) show the color of thearticles after initial cure. The articles on the bottom of FIG. 5(bottom-left and bottom-right) show the article after aging under astandard 25 Watt fluorescent office light (Trimline T8F25T8 SP35) atambient temperature for 30 days. The inventive examples demonstrategreatly improved color stability.

It was discovered that the examples that contained a thermochromiccomponent possessed a much more constant ΔE* over the 30 day test. Theseexamples were shown to have a ΔE* measured throughout the duration ofthe test that remained within 4% of the ΔE* measured on the first day ofthe test for the control condition, a ΔE* measured throughout theduration of the test that remained within 7% of the ΔE* measured on thefirst day of the test for the fluorescent light condition, and a ΔE*measured throughout the duration of the test that remained within 10% ofthe ΔE* measured on the first day of the test for the natural lightcondition. The percentage change was calculated by calculating thedifference of the ΔE* measured on a particular date and the ΔE* measuredon the first day, and dividing the result by the ΔE* measured on thefirst day, and multiplying by 100.

TABLE 3 Example 1 Example 4 Comparative Example 1 Clear Pink Clear PinkClear Pink Day L a B L a b ΔE* L a b L a b ΔE* L a b L a b ΔE* 0 84.52.0 6.9 60.0 37.4 −16.2 48.9 83.1 2.7 4.8 56.9 40.3 −16.8 50.6 87.6 −0.49.6 42.0 59.5 −5.4 76.7 2 83.1 2.7 4.6 57.1 40.0 −16.8 50.3 84.2 1.8 6.960.3 37.6 −16.1 48.8 87.7 −0.4 9.1 42.3 60.3 −8.4 77.7 4 84.2 1.9 6.959.9 37.4 −16.1 48.8 83.2 2.7 4.7 57.2 40.0 −16.7 50.2 88.9 −0.2 9.242.5 61.1 −7.8 78.7 7 83.1 2.7 4.8 57.1 39.9 −16.6 50.1 84.1 2.0 6.960.1 37.6 −16.0 48.6 88.2 −0.1 9.1 42.7 61.5 −8.4 78.5 9 84.1 1.9 6.960.3 37.4 −15.9 48.5 83.3 2.7 4.8 57.2 39.8 −16.6 50.2 88.4 −0.3 9.242.5 60.9 −8.1 78.5 11 84.1 2.0 7.0 60.1 37.4 −16.0 48.5 83.2 2.7 4.857.1 39.8 −16.7 50.2 87.1 −0.1 8.9 42.4 60.2 −8.3 77.0 14 83.7 2.2 6.760.1 37.7 −16.0 48.4 82.9 2.8 4.6 56.9 40.0 −16.7 50.1 88.4 0.1 9.0 42.961.5 −8.8 78.5 16 83.9 2.0 6.8 60.1 37.5 −15.9 48.5 83.1 2.8 4.8 57.239.7 −16.6 49.9 87.2 0.0 8.9 42.6 60.5 −8.5 77.1 18 83.8 2.1 6.8 60.037.7 −16.0 48.4 83.1 2.9 4.7 57.0 40.0 −16.7 50.2 87.2 0.2 8.8 42.8 60.8−8.8 77.2 21 84.0 2.0 6.8 59.9 37.5 −15.9 48.5 83.1 2.8 4.8 57.0 39.7−16.6 50.0 88.3 0.1 9.0 42.8 61.4 −8.8 78.4 23 83.8 2.1 6.7 60.0 37.7−16.0 48.5 83.1 2.8 4.7 57.0 39.9 −16.7 50.2 88.3 0.2 8.9 43.0 61.6 −9.078.3 25 83.9 2.3 6.6 59.9 37.6 −16.0 48.4 83.0 2.9 4.7 57.0 39.9 −16.650.0 87.0 0.2 8.7 42.8 60.8 −9.1 77.1 28 83.9 2.1 6.6 60.0 37.7 −16.048.5 83.1 2.8 4.7 56.9 39.9 −16.7 50.2 87.1 0.1 8.8 42.8 60.7 −9.0 77.230 83.9 2.2 6.6 59.9 37.6 −16.0 48.4 83.1 2.9 4.7 56.9 40.0 −16.7 50.187.1 0.2 8.7 42.8 60.8 −9.2 77.2

TABLE 4 Example 2 Example 5 Comparative Example 2 Clear Pink Clear PinkClear Pink Day L a B L a b ΔE* L a b L a b ΔE* L a b L a b ΔE* 0 84.21.7 7.0 59.8 38.0 −16.3 49.5 82.7 2.8 4.8 56.5 39.9 −16.6 50.2 88.2 −0.59.9 43.0 60.9 −6.5 78.1 2 83.9 2.1 6.6 59.6 37.7 −16.0 48.6 82.7 2.9 4.656.7 39.8 −16.4 49.7 80.6 12.8 1.4 42.9 61.1 −8.8 62.1 4 83.7 2.2 6.559.7 37.6 −15.8 48.2 82.4 3.0 4.5 56.6 39.8 −16.5 49.6 72.9 30.7 −9.342.3 60.3 −7.7 42.7 7 83.6 2.6 6.3 59.6 37.8 −15.7 48.0 82.2 3.2 4.556.8 39.9 −16.3 49.3 65.1 45.2 −17.3 41.9 59.5 −6.4 29.4 9 83.6 2.5 6.359.6 37.6 −15.6 47.9 82.2 3.2 4.5 56.7 39.8 −16.2 49.2 61.4 52.2 −20.841.6 59.2 −6.0 25.7 11 83.6 2.4 6.4 59.6 37.4 −15.4 47.7 82.2 3.1 4.656.7 39.6 −16.0 49.0 59.7 55.1 −22.2 41.5 59.1 −6.1 24.6 14 83.2 2.8 6.259.6 37.6 −15.2 47.2 82.0 3.3 4.6 56.6 39.7 −15.8 48.9 56.7 58.3 −23.141.4 58.3 −5.4 23.4 16 83.4 2.7 6.3 59.5 37.4 −15.1 47.3 82.0 3.3 4.656.5 39.7 −15.8 48.8 55.5 60.7 −23.6 41.3 58.5 −4.8 23.7 18 83.4 2.6 6.359.4 37.5 −15.1 47.4 82.0 3.4 4.6 56.5 39.7 −15.7 48.8 55.2 62.4 −24.241.1 58.2 −4.4 24.7 21 83.5 2.6 6.5 59.8 37.2 −14.8 47.0 82.1 3.3 4.856.5 39.2 −15.4 48.5 52.9 61.9 −23.6 40.7 57.1 −3.9 23.6 23 83.4 2.7 6.459.6 37.4 −14.8 47.1 82.1 3.4 4.7 56.7 39.6 −15.5 48.6 52.5 63.9 −23.740.9 57.8 −3.8 23.8 25 83.2 2.7 6.3 59.6 37.6 −14.9 47.1 82.0 3.4 4.756.6 39.5 −15.3 48.5 50.7 63.7 −23.6 40.6 56.8 −3.3 23.7 28 83.3 2.7 6.459.7 37.4 −14.7 46.9 82.0 3.3 4.7 56.5 39.2 −15.2 48.3 49.8 63.5 −22.440.4 56.5 −2.7 22.9 30 83.2 2.9 6.4 59.6 37.4 −14.5 46.7 82.0 3.4 4.856.6 39.4 −15.1 48.3 49.9 65.8 −23.5 40.5 57.0 −3.0 24.2

TABLE 5 Example 3 Example 6 Comparative Example 3 Clear Pink Clear PinkClear Pink Day L a B L a b ΔE* L a b L a b ΔE* L a b L a b ΔE* 0 84.61.8 6.7 59.8 38.0 −16.3 49.5 82.2 3.0 4.5 56.0 40.2 −16.6 50.1 88.4 −0.59.7 42.9 60.5 −6.0 77.8 2 84.4 2.3 6.6 59.8 37.9 −15.8 48.7 82.2 3.2 4.956.4 39.7 −15.9 49.2 84.9 4.8 7.0 42.5 59.7 −6.2 70.6 4 84.2 2.5 6.559.6 37.8 −15.1 48.1 81.7 3.4 5.0 56.3 39.5 −15.2 48.5 75.8 21.7 −1.141.8 58.0 −3.0 49.8 7 83.9 2.7 6.7 59.4 37.7 −14.4 47.7 81.5 3.7 5.456.2 39.4 −14.4 48.0 68.1 36.7 −6.9 41.6 57.3 −0.3 34.2 9 81.4 3.7 5.556.0 39.3 −14.0 47.8 81.4 3.7 5.5 56.0 39.3 −14.0 47.8 62.4 46.6 −10.741.5 57.0 −0.3 25.5 11 83.7 2.9 7.0 59.2 37.5 −13.7 47.1 81.2 3.7 5.755.9 39.2 −13.6 47.7 58.3 52.9 −12.9 41.1 56.5 0.1 21.9 14 83.5 3.1 7.059.1 37.6 −13.4 46.9 81.0 4.0 5.7 55.9 39.3 −13.3 47.3 55.3 58.1 −17.240.8 56.0 1.0 23.3 16 83.3 3.2 7.2 59.0 37.6 −13.1 46.7 80.7 4.1 5.955.7 39.3 −13.0 47.2 53.1 59.2 −14.6 40.3 54.4 3.9 23.0 18 83.1 3.4 7.458.8 37.6 −12.5 46.4 80.6 4.2 6.1 55.6 39.3 −12.4 46.9 51.3 59.8 −12.940.2 54.4 3.9 20.8 21 82.9 3.4 7.9 58.6 37.2 −11.4 45.8 80.4 4.4 6.655.4 38.9 −11.4 46.3 49.2 59.8 −10.8 39.7 53.6 4.9 19.4 23 82.8 3.6 7.958.4 37.7 −11.2 46.1 80.2 4.6 6.6 55.3 39.2 −11.2 46.3 49.4 60.8 −12.139.8 53.6 4.7 20.6 25 82.6 3.7 7.9 58.2 37.7 −11.1 46.0 79.9 4.7 6.855.1 39.3 −11.0 46.2 47.0 60.3 −9.2 39.2 52.5 7.3 19.8 28 82.4 4.0 8.257.9 37.8 −10.5 45.7 79.7 5.1 6.9 54.5 39.4 −10.4 45.9 45.7 60.0 −8.139.2 52.1 7.1 18.3 30 82.2 3.9 8.2 57.9 37.8 −10.3 45.6 79.6 5.0 7.054.9 39.2 −10.2 45.6 45.7 60.5 −8.9 39.2 52.3 6.5 18.7

Additional example compositions are made by adding 0.05 wt % ofexpandable microspheres (Expancel® 031 DUX 40) to commercially availableSOMOS® WaterClear® Ultra 10122 liquid radiation curable resin and thenmixed in a mixer for approximately 30 minutes until combined.

Rectangular parts of size 3.0 in×0.25 in×1.5 in (7.62 cm×0.635 cm×3.81cm) are created. One half of this part (1.5 in×0.25 in×1.5 in or 3.81cm×0.635 cm×3.81 cm) is selected to be white while the other half isselected to be clear and colorless. The parts are built using a SLA 250stereolithography system manufactured by 3D Systems with a tripled Nd:YAG solid-state laser. The laser has a 355 nm wavelength, 40 ps pulseduration. 100 MHz pulse repetition rate giving an average power of 400mW. The beam diameter is 1 mm and has a 0.5 mrad divergence. The partsare built using a 0.006 (0.1524 mm) inch slice layer, varying the hatchspacing, hatch overcure and border overcure to change the exposure eachpart receives. The clear area of the parts is created using a 0.004 inchhatch spacing, −0.002 hatch overcure, 0.002 border overcure with 2additional borders. The white opaque area of the parts is created with a0.0025 inch hatch spacing, 0.006 hatch overcure, 0.010 border overcurewith 2 additional borders. The temperature of the resin in this machinecan be controlled by external heaters. The parts were made with a resinvat temperature of 30+/−4° C. The parts are cleaned using isopropanol,air dried, and undergo a post process cure of 30 minutes per side.

The formulas of the example compositions are shown in Table 6.

TABLE 6 Component Somos ® WaterClear Expancel ® 031 Example Ultra 10122DUX 40 7 99.95 0.05 8 99.95 0.05 9 99.95 0.05

Color stability is measured using a Macbeth Model 7000 Color EyeColorimeter in accordance with the method for color stability discussedabove. The change in the samples' color and contrast over time isrecorded. Table 7 represents fee control condition, Table 8 representsthe fluorescent light condition, and Table 9 represents the naturallight condition. A ΔE* of N/M means that no color readings were measuredon that day and, consequently, a ΔE* could not be calculated on thatday. Excellent ΔE* stability was achieved for the example compositionsin comparison to the poor ΔE* stability of the prior art compositions inComparative Example 1, 2, and 3. The ΔE* measured throughout the teststayed within 20% of the ΔE* measured on the first day of the test forall three light conditions.

TABLE 7 Example 7 Clear White Day L a b L a b ΔE* 0 73.1 −1.3 1.3 62.2−2.9 12.4 15.6 2 73.2 −1.3 1.4 62.2 −2.7 12.7 15.8 4 73.1 −1.3 1.5 61.5−2.6 13.0 16.5 7 73.0 −1.4 1.5 61.4 −2.5 13.6 16.7 9 73.1 −1.4 1.6 61.1−2.5 13.6 17.0 11 N/M N/M N/M N/M N/M N/M N/M 14 N/M N/M N/M N/M N/M N/MN/M 15 72.9 −1.4 1.7 61.4 −2.3 14.4 17.1 16 N/M N/M N/M N/M N/M N/M N/M18 N/M N/M N/M N/M N/M N/M N/M 21 73.1 −1.4 1.8 61.7 −2.3 14.7 17.2 2373.1 −1.4 1.8 61.8 −2.3 14.9 17.3 25 73.0 −1.4 1.8 61.1 −2.3 14.5 17.528 73.1 −1.4 1.8 61.2 −2.2 14.7 17.5 30 73.3 −1.4 1.9 61.2 −2.2 14.617.6

TABLE 8 Example 8 Clear White Day L a b L a b ΔE* 0 73.8 −1.3 1.6 61.7−2.9 11.8 16.0 2 73.8 −1.1 1.2 62.0 −2.6 10.8 15.3 4 73.5 −1.0 1.3 62.6−2.2 10.1 14.1 7 73.6 −1.0 1.4 61.4 −1.9 10.0 15.0 9 73.4 −0.9 1.5 61.4−1.8 10.2 14.8 11 N/M N/M N/M N/M N/M N/M N/M 14 N/M N/M N/M N/M N/M N/MN/M 15 73.3 −0.8 1.8 61.2 −1.4 9.9 14.6 16 N/M N/M N/M N/M N/M N/M N/M18 N/M N/M N/M N/M N/M N/M N/M 21 72.9 −0.7 2.0 62.6 −1.0 9.5 12.8 2372.9 −0.7 2.1 61.7 −0.9 9.6 13.5 25 72.8 −0.7 2.2 61.2 −0.8 9.7 13.9 2872.9 −0.6 2.3 60.9 −0.7 9.7 14.1 30 72.5 −0.6 2.3 60.9 −0.6 9.6 13.7

TABLE 9 Example 9 Clear White Day L a b L a B ΔE* 0 72.5 −1.3 1.5 62.6−2.9 13.3 15.5 2 72.4 −1.2 2.1 62.0 −1.6 12.2 14.4 4 71.9 −1.1 2.5 61.9−0.5 11.9 13.7 7 71.7 −1.0 3.2 61.1   0.8 11.6 13.6 9 71.2 −0.9 3.5 60.9  1.1 11.7 13.3 11 N/M N/M N/M N/M N/M N/M N/M 14 N/M N/M N/M N/M N/MN/M N/M 15 70.9 −0.4 4.1 59.7   2.8 11.3 13.6 16 N/M N/M N/M N/M N/M N/MN/M 18 N/M N/M N/M N/M N/M N/M N/M 21 70.4   0.1 5.1 60.2   4.1 11.812.9 23 70.0   0.4 5.2 59.0   4.5 11.8 13.5 25 70.0   0.6 5.5 58.7   4.811.7 13.6 28 69.5   1.2 5.8 58.6   5.6 11.8 13.3 30 69.3   1.3 6.1 57.4  5.8 11.9 14.0

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one of ordinaryskill in the art that various changes and modifications can be madetherein without departing from the spirit and scope of the claimedinvention.

1-18. (canceled)
 19. A liquid radiation curable composition for additivefabrication comprising: (a) at least one thermally sensitive visualeffect initiator selected from the group consisting of a thermochromiccomponent and a thermally sensitive transparency modifier; (b) fromabout 45 to about 70 wt % of epoxies; (c) from about 5 to about 20 wt %of acrylates; (d) from about 10 to about 25 wt % of oxetanes; (e) fromabout 5 to about 15 wt % of photoinitiators; and (f) from 0 to about 10wt % of additives; wherein the thermally sensitive visual effectinitiator has the ability to change in color, transparency, or both dueto a change in temperature, and the change in color, transparency, orboth due to the change in temperature is non-permanent.
 20. The liquidradiation curable composition for additive fabrication of claim 19,wherein the thermally sensitive visual effect initiator is athermochromic component, and is present in an amount from about 0.005 wt% to about 5 wt %.
 21. The liquid radiation curable composition foradditive fabrication of claim 19, wherein the thermally sensitive visualeffect initiator is a thermally sensitive transparency modifier, and ispresent in an amount from about 0.005 wt % to about 5 wt %.
 22. Theliquid radiation curable composition for additive fabrication of claim20, wherein the thermochromic component is present in an amount fromabout 0.005 wt % to about 2 wt %.
 23. The liquid radiation curablecomposition for additive fabrication of claim 21, wherein the thermallysensitive transparency modifier is present in an amount from about 0.005wt % to about 2 wt %.
 24. The liquid radiation curable composition foradditive fabrication of claim 20, wherein the thermochromic component ispresent in an amount from about 0.5 wt % to about 1 wt %.
 25. The liquidradiation curable composition for additive fabrication of claim 21,wherein the thermally sensitive transparency modifier is present in anamount from about 0.5 wt % to about 1 wt %.
 26. The liquid radiationcurable composition for additive fabrication of claim 24, furthercomprising acid-impermeable microcapsules and a halochromic component,wherein the thermochromic component and halochromic component arecontained within the acid-impermeable microcapsules.
 27. The liquidradiation curable composition for additive fabrication of claim 26,wherein the composition changes from a first color to substantiallycolorless when heated above an activation temperature, and changes fromsubstantially colorless to the first color when cooled below theactivation temperature.
 28. The liquid radiation curable composition foradditive fabrication of claim 26, wherein the composition changes from afirst color to no color when heated above an activation temperature, andchanges from no color to the first color when cooled below theactivation temperature.
 29. The liquid radiation curable composition foradditive fabrication of claim 26, further comprising a secondthermochromic component, such that the composition changes to a secondcolor when heated above a second activation temperature.
 30. A liquidradiation curable composition for additive fabrication comprising: (a)from about 0.005 wt % to about 2 wt % of at least one thermallysensitive visual effect initiator selected from the group consisting ofa thermochromic component and a thermally sensitive transparencymodifier; (b) from about 45 to about 70 wt % of epoxies; (c) from about10 to about 25 wt % of acrylates; (d) from about 5 to about 15 wt % ofoxetanes; (e) from about 5 to about 15 wt % of polyols; (f) from about 5to about 15 wt % of photoinitiators; and (g) from 0 to about 10 wt % ofadditives; wherein the thermally sensitive visual effect initiator hasthe ability to change in color, transparency, or both due to a change intemperature, and the change in color, transparency, or both due to thechange in temperature is reversible.
 31. The liquid radiation curablecomposition for additive fabrication of claim 30, wherein the thermallysensitive visual effect initiator is a thermochromic component, and ispresent in an amount from about 0.5 wt % to about 1 wt %.
 32. The liquidradiation curable composition for additive fabrication of claim 31,wherein the thermochromic component is encased in a microcapsule. 33.The liquid radiation curable composition for additive fabrication ofclaim 32, wherein the thermochromic component changes from a first colorto substantially colorless when heated above an activation temperature.34. The liquid radiation curable composition for additive fabrication ofclaim 33, wherein the thermochromic component changes from substantiallycolorless to the first color when cooled below the activationtemperature.
 35. The liquid radiation curable composition for additivefabrication of claim 32, wherein the thermochromic component changesfrom a first color to no color when heated above an activationtemperature.
 36. A three dimensional article made from the liquidradiation curable composition for additive fabrication of claim
 19. 37.A three dimensional article made from the liquid radiation curablecomposition for additive fabrication of claim
 30. 38. A threedimensional article made from the liquid radiation curable compositionfor additive fabrication of claim 35.